Please show how to solve in simplest way with work, if needed excel is acceptable:

A publicly traded firm had the following stock price series... Jan $61.22 Feb $56.69 Mar $57.87 Apr $62.80 May $64.22 Jun $63.98 Calculate the historical standard deviation of returns for the stock. a.) 5.74% b.) 7.20% c.) 6.85% d.) 4.47% e.) 7.55%