You have $150,000 to invest in stocks A, B, and C and T-bil. You have decided to invest $30,000 in stock A and $25,000 in stock B. To make a portfolio with 108% of systematic risk of the whole market, how much should you invest in stock C? The standard deviation of market returns is 0,2, and the covariances of returns with the market returns are 0.036 for stock A, 0.056 for stock B and 0.046 for stock C, respectively