Use the Information for the Question(s)below

Use the information for the question(s) below.
Tom's portfolio consists solely of an investment in Merck stock.Merck has an expected return of 13% and a volatility of 25%.The market portfolio has an expected return of 12% and a volatility of 18%.The risk-free rate is 4%.Assume that the CAPM assumptions hold in the market.
-Assuming that Tom wants to maintain the current expected return on his portfolio,then the minimum volatility that Tom could achieve by investing in the market portfolio and risk-free investment is closest to:

A) 20%.
B) 25%.
C) 22%.
D) 18%.