//
// Created by awake on 2026/5/14.
//
#include <bits/stdc++.h>
using namespace std;

// clang-format off
struct { auto operator()(auto &i) { cin >> i; } } IN; // NOLINT
struct { auto operator()(auto &i) { cout << i << ' '; } } OUT; // NOLINT
// clang-format on
#define IOS ios::sync_with_stdio(false),cin.tie(nullptr)// NOLINT
using ll = long long;       //NOLINT
template <typename T>
using vec = vector<T>; //NOLINT
#define int long long
#define endl '\n'

void solve()
{
    int n, k;
    cin >> n >> k;
    string s;
    cin >> s;
    vec<int> a(n);
    ranges::for_each(a, IN);

    auto check = [&](int x)
    {
        int cnt = 0;
        bool blue = false;
        for (int i = 0; i < n; i++)
        {
            if (a[i] > x)
            {
                if (s[i] == 'B')
                {
                    if (!blue)
                    {
                        cnt++;
                        blue = true;
                    }
                }
                else
                    blue = false;
            }

        }
        return cnt > k;
    };
    int l = 0, r = 1e9 + 1;
    auto ran = views::iota(l, r);
    auto ans = *ranges::partition_point(ran, check);
    cout << ans << endl;
}


signed main()
{
    IOS;
    int T;
    cin >> T;
    while (T--)
        solve();

    return 0;
}