A biologist measured the lengths of hundreds of cuckoo bird eggs. Use the relative frequency distribution in the table below to answer the questions following it.

Lengths of Cuckoo Bird Eggs

Length (in millimeters)	Percent of eggs
18.75–19.75	0.8
19.75–20.75	4.0
20.75–21.75	17.3
21.75–22.75	37.9
22.75–23.75	28.5
23.75–24.75	10.7
24.75–25.75	0.8

(a) What percent of the group of eggs was less than 24.75 mm long?
%

(b) What is the probability that one of the eggs selected at random was at least 21.75 mm long but less than 23.75 mm long?