Penn Central Electricity has existing assets that generate $$4$ in earnings per share. If the firm does not invest except to maintain existing assets, EPS is expected to remain constant at $$4$ a year. However, Penn Central can start next year with investing $$1$ per share a year in developing a newly discovered source for electricity generation. Each investment is expected to generate a permanent $25\%$ return. However, the source will be fully developed by the fifth year of investing in it$,$ which means that no more new investments are possible from year $6$ onwards. Investors require an $18\%$ rate of return.

What is the price$-$earnings $($P$/$E$)$ ratio?

What is the stock price if the firm would have had the same investment opportunity for $5$ years,but now while maintaining a $75\%$ dividend payout ratio during these five years?

What is the NPVGO if the firm has the investment opportunity in perpetuity maintaining a $25\%$ retention ratio?

If you could show the work and how to solve these problems that would be great, my class does not use excel.