Concept:A leap year has 366 days, which is 52 weeks and 2 extra days.Explanation:There are 52 Sundays in 52 weeks, so the extra 2 days must include a Sunday for 53 Sundays.The 2 extra days can be any of the 7 possible consecutive pairs starting from Sunday to Saturday.Favorable pairs containing Sunday: (Sunday, Monday) and (Saturday, Sunday).Thus, 2 favorable outcomes out of 7 equally likely possibilities.Probability = 72​.Answer:72​