Need handwritten step wise answers please.

3. The following are exercises on internal rates of return: a. An investment of $1,000 today will return $2,000 at the end of 15 years. What is its internal rate of return? b. An investment of $1,000 will return $500 at the end of each of the next 4 years. What is its internal rate of return? c. An investment of $1,000 today will return $800 at the end of 1 year, $500 at the end of 2 years, and $100 at the end of 3 years. What is its internal rate of return d. An investment of $1,000 will return $120 per year forever. What is its internal rate of return