No excel please and please show your work!

Problem 7-22 Tam buying a firm with an expected perpetual cash flow of $850 but am unsure of its risk. I think the beta of the firm is when the beta is really 1 how much more will offer for the firm than it is truly worth? Assume the risk free rate is 5% and the expected rate of return on the market is 20% (input the amount as a positive value.) Present value difference