WA in MAXDIFF

1 
var arr = '';
process.stdin.on('data',function(chunk){
   arr += chunk; 
});
process.stdin.on('end',function(){
    arr = arr.split('\n');
    let t = parseInt(arr[0]),i=1,line=1,n,k,nk,weights,a,son_weight,father_weight,j;
    while(i<=t){
        nk = arr[line++].split(' ');
        n = parseInt(nk[0]);
        k = parseInt(nk[1]);
        weights = arr[line++].split(' ');
        a = [];
        for(j=0;j<weights.length;j++){
            a[j] = parseInt(weights[j]);
        }
        a.sort((a, b) => a - b);
        son_weight = 0;father_weight = 0;
        for(j=0;j<n;j++){
            if((j+1) <= k) son_weight = son_weight + a[j];
            else father_weight = father_weight + a[j];
        }
        if(father_weight > son_weight) console.log(father_weight - son_weight);
        else console.log(son_weight - father_weight);
        i++;
    }
})

Can anyone let me know for which test case i might be failing?