Walter builds birdhouses. He spends $5 on the materials for each birdhouse. He can build one in 30 minutes. He is semi-retired but earns $8 per hour at the local hardware store. He can sell a birdhouse for $20 each.
An Accountant would calculate the total profit for one birdhouse to be
A) $7
B) $12
C) $11
D) $15