Digger Enterprises purchased equipment for $64,000. In addition, shipping charges of $800 were incurred to obtain the equipment. The company paid $5,000 to construct a foundation and install the equipment. The equipment is estimated to have a residual value of $6,000 at the end of its 5-year useful life. Using the straight-line method, what is the book value of the equipment at the end of the third full year of use?
a. $22,120
b. $28,400
c. $31,520
d. $25,520