John Howard., a student at the University of South Alabama, bought 6 bookcases for his dorm room. Each required unpacking of parts and assembly, which included some nailing and bolting. John completed the first bookcase in 5 hours and the second in 4 hours.

(a) What is his learning rate?

(b) Assuming the same rate continues, how long will the 3rd bookcase take?

(c) The 4th, 5th, and 6th cases?

(d) All 6 cases?