HCAGMAM1

#include <iostream>
using namespace std;
#define ll long long int
int main()
{
    ll t;
    cin >> t;
    while (t--)
    {

        ll x, y, i;
        cin >> x >> y;
        string s;
        cin>>s;
        int count = 0, ans = 0, work = 0;
        for (i = 0; i <=30; i++)
        {
            if (s[i] == '1')
            {
                count++;
            }
            else
            {
                if (count > ans)
                {
                    ans = count;
                }
                count = 0;
            }
        }
        for (i = 0; i <=30; i++)
        {
            if (s[i] == '1')
            {
                work++;
            }
        }
       
        cout<<x*work+y*ans<<endl;
    }
    return 0;
}