(Figure: Output Level) According to the rational rule, what output and price should the firm in the following example choose? Price Marginal cost $10 $8 $6 Firm demand curve $2 Marginal revenue 2 4 6 8 10 Quantity O quantity = 6; price = $6.00 O quantity = 4: price = $4.00 O quantity = 8; price = $9.00 O quantity = 4: price = $7.00