Alphatech is a potential acquisition target. Alphatech is not listed on public markets but you have gathered the following information about three other listed companies that are in the same industry and comparable in terms of risk profile. You have also found Alphatech's marginal tax rate, cost of debt and D/E ratio are 25%, 5.5% and 30% respectively. Assuming comparable companies have the same leverage ratio as Alphatech, current risk-free rate at 2.5% and the market risk premium at 4.5%. 

a) What is your estimate of Alphatech's WACC, using CAPM model and the information from the three comparable companies