PLEASE EXPLAIN HOW TO SOLVE ON EXCEL. THANK YOU.

There is a probability of 0.33 that there will be extremely cold weather this coming Winter. If it does, we expect investors of Star \& Bucks to achieve a return of 0.17. Else, investors may expect a lower return of 0.07. Can you estimate the standard deviation for investors of Star \& Bucks? Type your answer as decimal (i.e. 0.052 and not 5.2\%). Round your answer to the nearest four decimals if needed