Scenario 13-11 Walter Builds Birdhouses. He Spends $5 on the Materials for Materials

Scenario 13-11
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.
-Refer to Scenario 13-11. An accountant would calculate the total cost for one birdhouse to be

A) $5.
B) $8.
C) $9.
D) $13.