This question context is from the textbook Engineering Economic Analysis
Four years ago, Mr. Moneypenny purchased a rare coin for $1,000. Today he sold the coin for $5,000. If the annual inflation rate for the past 4 years has been at 5%, state here on Blackboard the after-tax real percent interest rate (in percent to 2 decimal places, e.g. 4.47% or 25.61%) for this investment. Assume the net capital gains tax rate is 15%.