(1) How many codes are possible? What probability should be assigned to each code? What probability should be assigned to the event that the code contains the number 3?

Question

For this problem, assume that a product code consists of a digit from the set {2,6,3} followed by 4 letters, not necessarily distinct, selected from the set {Q, C, K, S, O}. For example, 3OOQO is such a code.

Answer 1

(3)(5)(5)(5)(5) = ?