Answer:
The precise expected rate of return (ERR) can be calculated using the following formula:
ERR = (1 + MARR) x (1 - Tax Rate) / (1 - Tax + (Tax/100) * (1 - MARR))
We have MARR = 8%, tax rate = 30%, and total project cost = $26,388.
So,
ERR = (1 + 8%) * (1 - 0.3) / (1 - 0.3 + (0.9/100) * (1 - 8%))
ERR = (1.08) * (0.7) / (0.7 + 0.0816)
ERR ~= 11.24%
So the precise expected rate of return would be closest to 11%