Problem #WSP-000064

Problem

a) Two numbers, $a$ and $b$, are relatively prime and their product is equal to $60$. What could these numbers be? Find all the possibilities.
b) The GCD of two numbers, $c$ and $d$, is $18$ and their product is $2^4\times 3^5\times 7$. What could these numbers be? Find all the answers.