What assumption is made about reinvestment of cash flows in net present value calculations? In internal rate of return calculations?

What is the major difference between the internal rate of return approach and the present value approach?

Under what conditions might the internal rate of return yield multiple solutions?

Why would a lender charge a lower contract interest rate coupled with a front-end fee? Why not simply incorporate the effective rate into the contract rate?

If financial leverage is favorable, why would an investor want to repay a loan before its due date?