3 A forest consists of two types of trees: those that are 0–5 ft and those that are taller than 5 ft. Each year, 40% of all 0–5-

ft tall trees die, 10% are sold for $20 each, 30% stay between 0 and 5 ft, and 20% grow to be more than 5 ft. Each year, 50%

of all trees taller than 5 ft are sold for $50, 20% are sold for $30, and 30% remain in the forest.

a What is the probability that a 0–5-ft tall tree will die before being sold?

b If a tree (less than 5 ft) is planted, what is the expected revenue earned from that tree?