//Dynamic Programming
//time limit exceeds while using bottom up
//trying top down
//#define TOP

#include <stdio.h>
#include <iostream>

using namespace std;

//////////////////////////////////////////////////////////////////////////////////

int main(void)
{
    #ifdef TOP
    int optimize( int, int &, int *, int *, int * ); 
    #else
    void optimize( int &, int &, int *, int * );
    #endif 
    int number_of_test_cases = 0, counter_of_cases = 0;
    int weight_empty = 0, weight_filled = 0, varieties = 0, net = 0;
    int *value, *weight;
    scanf( "%d", &number_of_test_cases);
    
    for( counter_of_cases = 1; 
         counter_of_cases <= number_of_test_cases; 
         ++counter_of_cases)
    {
        scanf( "%d %d", &weight_empty, &weight_filled );
        scanf( "%d", &varieties );
        value = new int[ varieties + 3 ];
        weight = new int[ varieties + 3 ];
        net =  weight_filled - weight_empty;
        for( int counter = 1; counter <= varieties; ++counter )
        {
            scanf( "%d %d", &value[ counter ], &weight[ counter ] );
        }
        // for testing
        #ifdef TOP
        int *opt;
        int temp;
        opt = new int[ net + 1 ];
        for( int counter2 = 0; counter2 <= net + 1; counter2++ )
        opt[ counter2 ] = -1;
        opt[ 0 ] = 0;
        temp = optimize( net, varieties, value, weight, opt );
        if( temp == -1 )
        printf( "This is impossible.\n" );     
        else printf( "The minimum amount of money in the piggy-bank is %d.\n", temp ); 
        #else
        optimize( net, varieties, value, weight );
        #endif  
        // 
        delete value;
        delete weight;
        #ifdef TOP
        delete opt;
        #endif    
    }               
    return 0;
}

/////////////////////////////////////////////////////////////////////////////////

// bottom up
#ifndef TOP
void optimize( int &net, int &varieties, int *value, int *weight )
{
    int *opt;
    opt = new int[ net + 3 ];
    for( int counter = 0; counter <= net + 2; counter++ )
    opt[ counter ] = -1;
    opt[ 0 ] = 0;
    int temp;
    //Dynamic Programming
    for( int counter = 1; counter <= varieties; counter++)
    {
        for( int counter2 = net; counter2 >= weight[ counter ]; counter2-- )
        {
            for( int counter3 = 1; counter3 * weight[ counter ] <= counter2 ; counter3++ )
            {
                temp = opt[ counter2 - weight[ counter ] * counter3 ];
                /*if( opt[ counter2 ] == -1 && temp != -1 )   
                opt[ counter2 ] = temp + value[ counter ] * counter3;
                if( opt[ counter2 ] != -1 && temp != -1 )
                opt[ counter2 ] = 
                min( opt[ counter2 ], 
                opt[ counter2 - weight[ counter ] * counter3 ] + value[ counter ] * counter3 ); */
                if( temp == -1) continue;
                else if( opt[ counter2 ] == -1 ) opt[ counter2 ] = temp + value[ counter ] * counter3;
                else if( temp + value[ counter ] * counter3 < opt[ counter2 ] ) opt[ counter2 ] = temp + value[ counter ] * counter3;     
            }              
        }
    }
    if( opt[ net ] == -1 )
    printf( "This is impossible.\n" );     
    else printf( "The minimum amount of money in the piggy-bank is %d.\n", opt[ net ]);         
}

/////////////////////////////////////////////////////////////////////////////////

#else
// top down
int optimize( int net, int &varieties, int *value, int *weight, int *opt )
{
    if( opt[ net ] == -1)
    for( int counter1 = 1; counter1 <= varieties; counter1++)
    {
        for( int counter2 = 1; counter2 * weight[ counter1 ] <= net; counter2++ )
        {
            int temp = 
            optimize( net - weight[ counter1 ] * counter2, 
            varieties, value, weight, opt );
            if( temp == -1 ) continue;
            else if( opt[ net ] == -1 ) opt[ net ] = temp + value[ counter1 ] * counter2; 
            else if( temp + value[ counter1 ] * counter2 < opt[ net ] ) opt[ net ] = temp + value[ counter1 ] * counter2;  
        }    
    }
    return opt[ net ];
}
#endif