1. Explain how the following investment methods are used. a. net present value b. internal rate of return c. pay back period d. profitability index 2.state explain the advantages and disadvantages of the following a. net present value b. pay back period c. internal rate of return d. profitability index 3.Explain the following, clearly indicating the formula a. ordinary annuities and present values b. Due annuities and present values c. perpetuity and present values.