Use the following information to calculate total revenue, marginal revenue, and marginal cost. Indicate the profit-maximizing level of output. If the price was $3 and fixed costs were $5, what would variable cost be? At what level of output would the firm produce?

Output Price Total costs Total Revenue (P*Q)

              1     $5             $10

              2       5              12

              3       5              15

              4       5              19

              5       5              24

              6       5              30

              7       5              45