/////////////// ignore above this line ////////////////////

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();
        // <-- SOlution start -->
        let arr = []
        for(i=0;i< n;i++){
          let nums = Array.from(num,(a,b) => {
            while(b>=i && b< i+k) { 
            // Mapping Array if Index of number is Higher or Equal to the current loop index and less than the sum of K and current loop index
              return a
              }
          }).filter((a) => a!= undefined ) // Exclude Undefined
          if(nums.length == k) arr.push(nums.reduce((a,b) => a*b,1)) // Push Multiplied results if the array's length equals to K
        }
        console.log(arr.sort((a,b) => a-b)[arr.length-1])
        // <-- SOlution End -->
    }
}