#include<bits/stdc++.h>
using namespace std;
#define ll long long
ll T,a,b,c;
ll p[1001],s;
ll ans;
int main()
{
    scanf("%lld",&T);
    p[0]=1;
    for(int i=1;;i++)
    {
        p[i]=2*p[i-1];
        if(p[i]>=1e9)
        {
            s=i;
            break;
        }
    }
//    printf("%lld %lld\n",s,p[s]);
    while(T--)
    {
        scanf("%lld%lld%lld",&a,&b,&c);
        ans=0;
        for(ll i=0;i<=30;++i)
        {
            ll tmp;
            tmp=c/p[i];
            if(c%p[i]!=0) tmp++;
            if(ans==0) ans=a*i+tmp*b;
            else ans=min(ans,a*i+tmp*b);
            if(p[i]>=c) break;
        }
        printf("%lld\n",ans);
    }
}