```
package A;

import java.io.*;

public class Main {
    static int[] b;
    static StreamTokenizer st = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
    static PrintWriter pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
    private static int Int() throws Exception{
        st.nextToken();
        return (int)st.nval;
    }
    public static void main(String[] args) throws Exception{
        int t = Int();
        while (t-- > 0){
            int n = Int();
            int k = Int();
            b = new int[n];
            int[] add = new int[n + 1];//a前n项和
            for (int i = 0; i < n; i++) {
                add[i + 1] = add[i] + Int();
            }
            for (int i = 0; i < n; i++) {
                b[i] = Int();
            }
            int x = Math.min(n, k);
            int[] b1 = new int[x];//维护一个单调数组
            for (int i = 1; i < x; i++) {
                if(b[i] > b[b1[i - 1]]){
                    b1[i] = i;
                }else b1[i] = b1[i - 1];
            }
            int ans = 0;

            if(n > k){
                for (int i = 0; i < x; i++) {
                    int temp = add[i + 1] + (k - i - 1) * b[b1[i]];
                    ans = Math.max(ans, temp);
                }
            }else {
                for (int i = 0; i < x; i++) {
                    int temp = add[i + 1] + (k - i - 1) * b[b1[i]];
                    ans = Math.max(ans, temp);
                }
            }


            pw.println(ans);

        }
        pw.flush();
    }

}

```