Leslie, Inc., followed the practice of depreciating its building on a straight-line basis. A building was purchased in 2016 and had an estimated useful life of 25 years and a residual value of $20,000.
The company's depreciation expense for 2016 was $15,000 on the building.

What was the original cost of the building?
a. $395,000
b. $500,000
c. $520,000
d. Cannot be determined from the information given.