Diversification. Here are the returns on two stocks. $($

$\backslash$table$[[,$Digital Cheese,Executive Fruit$],[$January$,+15,+7],[$February$,-3,+1],[$March$,+5,+4],[$April$,+7,+13],[$May$,-4,+2],[$June$,+3,+5],[$July$,-2,-3],[$August$,-8,-2]]$

a$.$ Calculate the variance and standard deviation of each stock. Which stock is riskier if held on its own?

b$.$ Now calculate the returns in each month of a portfolio that invests an equal amount each month in the two stocks.

c$.$ Is the variance more or less than halfway between the variance of the two individual stocks?