A graph is set up with "yearly depreciation expense" on the vertical axis and "time" on the horizontal axis. Assuming linear relationships, how would the graphs for straight-line and sum-of-the-years'-digits depreciation, respectively, be drawn?
a. Vertically and sloping down to the right
b. Vertically and sloping up to the right
c. Horizontally and sloping down to the right
d. Horizontally and sloping up to the right
Answer: C