C :

#include<stdio.h>
int main(){
	int n;
	double m,s=0.0;
	scanf("%d%lf",&n,&m);
	if(n<=40) s=n*m;
	if(n>40 && n<=50) s=40*m+(n-40)*1.5*m;
	if(n>50) s=40*m+15*m+(n-50)*2*m;
	printf("%.2f",s);
	return 0;
}

C++ :

#include <bits/stdc++.h>
using namespace std;
int main(){
   int i;
   cin>>i;
   double s,t,a;
   cin>>a;
   if(i <= 40){
   	 t = i * a;
   }else if(i > 40 && i <= 50){
   	 s = i - 40;
   	 t = a * 40 + a * 1.5 * s;
   }else if(i > 50){
   	 s = i - 50;
   	 t = a * 40 + a * 1.5 * 10 + a * 2 * s;
   }
   cout<<fixed<<setprecision(2)<<t<<endl;
   return 0;
}

Java :

import java.util.Scanner;
public class Main{
public static void main (String[] args){
	Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();			
		double m = sc.nextDouble();
		    double s = 0.0;
		    if(n <= 40) {
		        s = n * m;
		    }else if(n <= 50 && n > 40) {
		        s = m * 40 + (n - 40) * m * 1.5;
		    }else if(n > 50) {
		        s = m * 40 + 10 * m * 1.5 + (n - 50) * 2 * m;
		    }
		    System.out.println(String.format("%.2f",s));
		
	 }
		
				
     }