A 3-column table has 7 rows. The first column is labeled Bikes produced per day with entries 1, 2, 3, 4, 5, 6, 7. The second column is labeled total cost with entries 80, 97, 110, 130, 160, 210, and 270. The third column is labeled Marginal cost with all blank entries. Using this table, calculate the marginal cost of each of these quantities of bikes. The first bike: $ The fourth bike: $ The sixth bike: $ The seventh bike: $