Smartphone problem -few test cases are failing

Could anyone please suggest why the following code is failing dew test cases while other test cases are running fine? What exactly is being checked in test cases 7-14? They are failing.
/* 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
{

	Scanner scanner = new Scanner(System.in);
	int noOfPotentialCustomers = 0;
	noOfPotentialCustomers = scanner.nextInt();
	if (noOfPotentialCustomers >= 1 && noOfPotentialCustomers <= 5000) {
		long[] custRate = new long[noOfPotentialCustomers];		
		for (int i = 0; i < noOfPotentialCustomers; i++) {
			custRate[i] = scanner.nextLong();
			
		}
		System.out.println(maxPrice(custRate));
	}

	scanner.close();

}
private static long maxPrice(long[] custRate) {		

	Arrays.parallelSort(custRate);
	long maxprice = 0;
	for (int i = 0, k = custRate.length; i < custRate.length && k > 0; i++, k--) {

		long max = custRate[i] * k;
		if (max > maxprice)
			maxprice = max;
	}

	return maxprice;

}

}