The following is return data for a retail sector ETF and energy sector ETF for the years 2015 to 2019.

Year	Retail Sector ETF	Energy Sector ETF
2015	−0.27	0.45
2016	−0.31	−0.44
2017	0.72	0.33
2018	0.29	0.13
2019	0.1	−0.03

a. What is the arithmetic mean return for each ETF?

b. What is the sample standard deviation for each ETF? Which ETF was riskier over this time period?

c. Given a risk-free rate of 5%, what is the Sharpe ratio for each ETF? Which investment had a better return per unit of risk over this time period?