Final answer:
The correct function to input in cell B8 to forecast the number of payments for a loan in Excel is =NPER(B8, B6, -B5).
Step-by-step explanation:
In cell B8 on the Payment Calculator worksheet, the function to forecast the number of payments required to pay off the loan using information from column B is =NPER(B8, B6, -B5). This function, NPER, stands for "number of periods" and is used to calculate the duration, in terms of number of periods, required to pay off a loan based on periodic, constant payments and a constant interest rate. It takes three arguments: rate, payment, and present value, hence why B6 is used as it likely represents the periodic interest rate, and B5, probably representing the present value or initial loan amount, is negated to indicate a loan being paid off.
The provided calculations show the implications of interest rate changes on the present value of future dollar payments. When the interest rate goes from 8% to 11%, the present value of a bond decreases because the discount rate has increased, meaning someone selling the bond at the higher interest rate would likely find the value of their investment has decreased.