In the game of blackjack you are dealt two cards from a standard playing deck. Your score is the sum of the value of the two cards, where numbered cards have the value given by their number, face cards (Jack, Queen, King) each receive 10 points, and an Ace either 1 or 11 (player can choose). A blackjack is receiving a score of 21 fromtwo cards, thus an Ace and any card worth 10 points.

(a) What is the probability of receiving a blackjack?

(b) The dealer is dealt one of his cards face down and one face up. Suppose the “show” card is an Ace.

What is the probability the dealer has a blackjack? (For simplicity assume you have not seen any other cards.)