public static long kadane(long arr[]) {

int n = arr.length;

long cs = 0, mx = Integer.MIN_VALUE;

for (int i = 0; i < n; i++) {

cs += arr[i];

if (cs < 0)

cs = 0;

else

mx = Math.max(mx, cs);

}

return mx;

}

public static long accumulate(long arr[]) {

long sum = 0;

for (int i = 0; i < arr.length; i++) {

sum += arr[i];

}

return sum;

}

public static void main(String[] args) throws java.lang.Exception {

int t;

Scanner sc = new Scanner(System.in);

t = sc.nextInt();

while (t-- > 0) {

int n, k;

n = sc.nextInt();

k = sc.nextInt();

long arr[] = new long[n];

for (int i = 0; i < n; i++) {

arr[i] = sc.nextLong();

}

long maxsum = kadane(arr);

if (k == 1) {

System.out.println(maxsum);

} else {

long total = accumulate(arr);

long prefix = 0, suffix = 0, p = 0, s = 0;

for (int i = 0; i < n; i++) {

p += arr[i];

s += arr[n - i - 1];

prefix = Math.max(prefix, p);

suffix = Math.max(suffix, s);

}

if (total > 0) {

maxsum = Math.max((((k - 2) * total) + prefix + suffix), maxsum);

System.out.println(maxsum);

} else {

System.out.println(prefix + suffix);

}

}

}

}