Alice is telling Bob that he should use a pair of the form (3, n) or (16385, n) as his RSA public key, where, as usual, n = pq, for two large primes, p and q, if he wants people to encrypt messages for him from their cell phones. What is the justification for Alice's advice?

What will be an ideal response?

The numbers 3 and 16385 are relatively easy to use as exponents in the repeated
squaring algorithm. So it will be easier for a cell phone to encrypt messages to Bob using
his RSA public key in these cases.