hdu5280dp

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StreamTokenizer;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Scanner;
import java.util.Stack;
import java.util.StringTokenizer;

public class Main {

public static void main(String[] args) throws IOException{
StreamTokenizer cin = new StreamTokenizer(new BufferedInputStream(System.in));
InputReader in = new InputReader(System.in)  ;
PrintWriter out = new PrintWriter(System.out) ;
int t = in.nextInt() ;

while((t--) > 0){
new Task().solve(in , out)  ;

//  out.flush() ;
}

out.flush() ;
}

}

class  Task{

long[] a , dp1 , dp2 ;

public  void  solve(InputReader in , PrintWriter out){
int n = in.nextInt() ;
int p = in.nextInt() ;
a = new long[n+2] ;
dp1 = new long[n+2] ;
dp2 = new long[n+2] ;
for(int i = 1 ; i <= n ; i++) a[i] = in.nextLong() ;

dp1[0] = 0 ;
for(int i = 1 ; i <= n ; i++)
dp1[i] = Math.max(dp1[i-1] + a[i], a[i]) ;

dp2[n+1] = 0 ;
for(int i = n ; i >= 1 ; i--)
dp2[i] = Math.max(dp2[i+1] + a[i] , a[i]) ;

long ans = Long.MIN_VALUE ;

for(int i = 1 ; i <= n ; i++){
ans = Math.max(ans , Math.max(0 ,dp1[i-1]) + p + Math.max(0 , dp2[i+1]) ) ;
}

for(int i = 1 ; i < n ; i++) ans = Math.max(ans, dp1[i]) ;
for(int i = 2 ; i <= n ; i++) ans = Math.max(ans, dp2[i]) ;

out.println(ans) ;
}
}

class InputReader{
public BufferedReader reader;
public StringTokenizer tokenizer;

public InputReader(InputStream stream){
reader = new BufferedReader(new InputStreamReader(stream), 32768);
tokenizer = null;
}

public String next(){
while(tokenizer == null || !tokenizer.hasMoreTokens()){
try{
tokenizer = new StringTokenizer(reader.readLine());
}catch (IOException e) {
throw new RuntimeException(e);
}
}
return tokenizer.nextToken();
}

public int nextInt() {
return Integer.parseInt(next());
}

public long nextLong() {
return Long.parseLong(next());
}

}