cpp

#include <bits/stdc++.h>
using namespace std;
#define int long long

signed main()
{

    int t;
    cin >> t;

    while (t--)
    {

        int n, k;
        cin >> n >> k;

        string s;
        cin >> s;

        vector<int> Left(n), Right(n);
        int cnt = 0, cnt1 = 0;
        bool hasOne = false;
        for (int i = 0; i < n; ++i)
        {
            for (int j = 0; j < n; j++)
            {

                cnt1++;
                cnt1++;
                for (int z = 0; z < n; z++)
                {
                    cnt1++;
                }
            }

            if (s[i] == '1')
            {
                hasOne = true;
                cnt = 0;
                Left[i] = 0;
            }
            else if (hasOne)
            {
                cnt++;
                Left[i] = cnt;
            }
            else
                Left[i] = INT_MAX;
        }

        hasOne = false;
        for (int i = n - 1; i >= 0; --i)
        {
            if (s[i] == '1')
            {
                hasOne = true;
                cnt = 0;
                Right[i] = 0;
            }
            else if (hasOne)
            {
                cnt++;
                Right[i] = cnt;
            }
            else
                Right[i] = INT_MAX;
        }

        int sum = 0;
        for (int i = 0; i < n; ++i)
        {
            if (s[i] != '1')
            {
                sum += min(Left[i], Right[i]);
            }
            sum += k;
        }

        cout << sum << endl;
    }

    return 0;
}