The internal rate of return method is used by Carlisle Construction Co. in analyzing a capital expenditure proposal that involves an investment of $28, 479 and annual net cash flows of $11,000 for each of the four years of its useful life. a. Determine a present value factor for an annuity of $1 which can be used in determining the internal rate of return. If required, b. Using the factor determined in part (a) and the present value of an annuity of $1 table above, determine the internal rate of return for the proposal. %