How do I solve this???

Suppose Francine Dunkleberg's Sweets is considering investing in warehouse management software that costs $500,000, has $70,000 residual value, and should lead to cost savings of $125,000 per year for its five-year life. In calculating the ROR, which of the following figures should be used as the equation's denominator (average amount invested in the asset)?

a) $570,000

b) $215,000

c) $285000

d)$250000