function greatestProduct (n,k,num) {
    let product = 0;
  arrayOfEl = num.split("");

  for (let i = 0; i <= n - k; i++) {
    const multiplication = arrayOfEl
      .slice(i, k + i)
      .reduce((acc, curr) => (acc *= curr));
    if (multiplication > product) product = multiplication;
  }
  console.log(product);
}

function main() {
    var t = parseInt(readLine());
    for(var a0 = 0; a0 < t; a0++){
        var n_temp = readLine().split(' ');
        var n = parseInt(n_temp[0]);
        var k = parseInt(n_temp[1]);
        var num = readLine();
        greatestProduct(n,k,num)
    }