$15.$ Using the data in the following table, calculate the return for investing in this stock from January $1$ to December $31.$ Prices are after the dividend has been paid. $16.$ Consider the following five monthly returns: a$.$ Calculate the arithmetic average monthly return over this period. b$.$ Calculate the geometric average monthly return over this period. c$.$ Calculate the monthly variance over this period. d$.$ Calculate the monthly standard deviation over this period. $17.$ Explain the difference between the arithmetic average return you calculated in Problem $16$a and the geometric average return you calculated in Problem $16$b$.$ Are both numbers useful? If so$,$ explain why.