Buy Lamp Codechef problem solution

Buy Lamps Codechef Problem Solution

An electronics shop sells red and blue lamps. A red lamp costs $X$ rupees and a blue lamp costs $Y$ rupees.

Chef is going to buy exactly $N$ lamps from this shop. Find the minimum amount of money Chef needs to pay such that at least $K$ of the lamps bought are red.

Input Format

The first line of input will contain a single integer $T$ , denoting the number of test cases.
Each test case consists of a single line containing four space-separated integers $N, K, X, Y$

Output Format

For each test case, output on a new line the minimum amount of money Chef needs to pay in order to buy $N$ lamps such that at least $K$ of the lamps bought are red.

Constraints

$1 \leq T \leq 10^{3}$
$1 \leq N \leq 10^{8}$
$0 \leq K \leq N$
$1 \leq X, Y \leq 10$

Sample Input 1

Sample Output 1

Explanation

Test case $1$ : Chef buys $2$ red lamps with $2 \cdot 5 = 10$ rupees.

Test case $2$ : Chef buys $1$ red lamp and $3$ blue lamps with $1 \cdot 3 + 3 \cdot 1 = 6$ rupees.

Test case $3$ : Chef buys $3$ red lamps with $3 \cdot 4 = 12$ rupees.

				
					/* package codechef; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Codechef
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		
		Scanner sc=new Scanner(System.in);
		int t=sc.nextInt();
		while(t-->0){
		    int n=sc.nextInt();
		    int k=sc.nextInt();
		    int x=sc.nextInt();
		    int y=sc.nextInt();
		
		    int r=n-k;
		    int ans = k*x;
		    
		    int a=x<y?x:y;
		    ans+=r*a;
		    
		    System.out.println(ans);
		}
		
	
		
	
	}