The cooler: your local corner supermarket tends to be a bit negligent about checking their stock, and you know from experience that one in five milk cartons is past its sell-by date. Earlier today, you bought a carton of milk, and forgot to check the date.

(a) What is the frequentist probability that your milk is past its sell-by date?

(b) What is the objective Bayesian probability that your milk is past its sell-by date?