A small engineering firm has $100,000 set aside in a capital improvement fund to purchase new equipment. If $30,000 is invested at 30%, $20,000 at 25%, and the remaining $50,000 at 20% per year, the overall rate of return on the entire $100,000 is estimated to:

Select one: a. 24 % per year b. 16 % per year c. 22 % per year d. 28 % per year