Computing internal rate of return. Compute the internal rate of return for each of the following projects, each of which requires an initial investment of $100. 000 and provides the periodic cash flows indicated.

a. $23,098 per period for 5 periods.

b. $20,336 per period for 6 periods.

c. $17,401 per period for 8 periods.

d. $16,144 per period for 12 periods.

e. $17,102 per period for 15 periods.