Your portfolio is comprised of 20% of stock X, 40% of stock Y, and the rest in stock Z. Stock X has an expected return of 12% and stock Y has an expected return of 20%. If the portfolio has an...

Your portfolio is comprised of 20% of stock X, 40% of stock Y, and the rest in stock Z. Stock X has an expected return of 12% and stock Y has an expected return of 20%. If the portfolio has an expected return of 18%, what is the expected return of stock Z?