Suppose we have the following returns for large-company stocks and Treasury bills over a six year period:

year	Large company	US treasury bill
1	3.90	5.84
2	14.47	2.49
3	19.21	3.72
4	-14.47	7.14
5	-31.96	5.26
6	37.45	6.39

a. Calculate the arithmetic average returns for large-company stocks and T-bills over this period. (Round your answers to 2 decimal places. (e.g., 32.16))

Average returns

Large company stocks % ANSWER 4.8

T-bills % 5.1

b. Calculate the standard deviation of the returns for large-company stocks and T-bills over this period. (Do not round intermediate calculations and round your final answers to 2 decimal places. (e.g., 32.16))

Standard deviation

Large company stocks % ANSWER 24.86

T-bills % ANSWER 1.74

c-1 Calculate the observed risk premium in each year for the large-company stocks versus the T-bills. What was the average risk premium over this period? (Negative amount should be indicated by a minus sign. Do not round intermediate calculations and round your final answer to 2 decimal places. (e.g., 32.16))

Average risk premium % ANSWER: -.37

c-2 Calculate the observed risk premium in each year for the large-company stocks versus the T-bills. What was the standard deviation of the risk premium over this period? (Do not round intermediate calculations and round your final answer to 2 decimal places. (e.g., 32.16))

Standard deviation % ??

I just need help figuring out the standard deviation of the risk premium