Calculate the arithmetic average returns for large-company

Question

Consider the following rates:

Year Large Company Stocks       US Treasury Bills

1                     3.98%                                       4.56%  

2                    14.33                                      4.92

3 19.17                                       3.84

4                     -14.51                                       6.98

5                     -32.00                                        5.22

6                      37.41                                        5.36

A. Calculate the arithmetic average returns for large-company stocks and T-bills over this period

Avg. Returns

Large Company Stock                7.59?

T-bills                                           3.87

B. Calculate the standard deviation of the returns for large-company stocks and T-bills over this period

Standard Deviation

Large-company stocks      4.72

T-bills 3.31?

Where am I off on these? What equations would I use to find these numbers?