PermutationSend FeedbackGiven two values, n and r, write a function to calculate the permutation (nPr) for n ≥ r ≥ 0. The function should return -1 if n < r or if n or r are negative. The program should include two functions: one to calculate the factorial of a number and another to calculate the permutation.Function Input:n (int): The total number of objects.r (int): The number of objects taken at a time for the permutation.Output:The function will return the calculated permutation (nPr) in integer format. Handle input cases where r is greater than n. The function will return "please enter n >= r >= 0".Sample Input 16 5 Sample Output 1720Sample Input 25 6Sample Output 2please enter n >= r >= 0

The problem is asking to write a function that calculates the permutation of given two numbers. Permutation is the arrangement of objects without considering the order. The formula for permutation is nPr = n! / (n-r)!.

Here is a Python solution for the problem:

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n-1)

def permutation(n, r):
    if n < r or n < 0 or r < 0:
        return "please enter n >= r >= 0"
    else:
        return factorial(n) / factorial(n-r)

# Test the function
print(permutation(6, 5))  # Output: 720
print(permutation(5, 6))  # Output: "please enter n >= r >= 0"

In this solution, we first define a helper function factorial to calculate the factorial of a number. Then we define the main function permutation to calculate the permutation. If the input is invalid (n < r or n < 0 or r < 0), the function returns a string "please enter n >= r >= 0". Otherwise, it calculates the permutation using the formula and returns the result.