A phonetic password generator picks two segments randomly for each six letter password. form is CVC. what is the total password population?

We have 4 times C and 2 times V.
Repetition is allowed.
That sums up the possibilities:
C^4*V^2 with C=21 and V=5
= 4,862,025
A fully random 6-letter-passWord would be almost 64 times stronger.

A team of six students traveled to a mathematics competition by bicycle. On leaving, they distractedly picked up their six helmets at random (each choice of helmet is equally likely). What is the probability that exactly three of the students picked up the correct helmet?
can you explain why? and show the work??