Portfolio risk and return

Ariel holds a $$7,500$ portfolio that consists of four stocks. Her investment in each stock, as well as each stock's beta, is listed in the following table:

Suppose all stocks in Ariel's portfolio were equally weighted. Which of these stocks would contribute the least market risk to the portfolio?

Mainway Toys Co$.$

Omni Consumer Products Co$.$

Suppose all stocks in the portfolio were equally weighted. Which of these stocks would have the least amount of stand$-$alone risk?

Kulatsu Motors Co$.$

Three Waters Co$.$

Kulatsu Motors Co$.$

Three Waters Co$.$

Mainway Toys Co$.$

Omni Consumer Products Co$.$