Jethro wants a swimming pool in his backyard, so he digs a rectangular hole with dimensions 40 feet long, 20 feet wide, and 5 feet deep. how many cubic feet of water will the pool hold?

You just need to find the capacity (volume) of the swimming pool.
Volume = length x width x depth
             = 40 x 20 x 5
             = 4000 
The pool will hold 4,000 cubic feet of water.