A portfolio has 45% of its funds invested in Security C and 55% of its funds invested in Security D. Security C has an expected return of 9% and a standard deviation of 9%. Security D has an expected return of 9.6% and a standard deviation of 10.2%. The securities have a coefficient of correlation of -0.2. Calculate the portfolio standard deviation. PLEASE SHOW ALL WORK. USE EXCEL IF POSSIBLE.