Write a postfix operator isPrime that is true when the operand is a prime number. You will need to write a rule to determine if a number is prime or not. You must use your operator from part a) You do not need to worry about efficiency for this question. There are many sophisticated ways to find prime numbers but a simple brute force check will suffice (it should work for any number though) ?- prime (2) ?- prime (4) 2- prime (7) true. false. true. ?- prime(997) true.