7. XXX company has forecast a rate of return of 20% if the economy booms (30% probability); a rate of return of 19% if the economy in in a growth phase (40% probability); a rate of return of 2.50% if the economy in in decline (20% probability); and a rate of return of -10% if the economy in a depression (10% probability). What is the company standard deviation of returns? (3 Marks)