VGTU_ACM_ICPC_A

// VGTU ACM ICPC selection A
#include <iostream>
using namespace std;
int main()
{
    long long int t, k, p, n, z;
    cin >> t;
    for(int i=0;i<t;i++)
    {
        cin >> k >> p >> n;
        if(k>=p){z = k-p;}
        else{z=0;}
        cout << z*n << endl;
    }
    return 0;
}