An airplane company is determining the difference in selling price if rows of first-class seats are added to a new design. Using the average selling price of $1,000 per first-class seat, the total selling price for one new row is
f(r) = 4,000r. Each row in first class eliminates two rows of economy seats. Using the average selling price of $150 per economy seat, the total price for each pair of removed rows is e(r) = 1,800r.

which is d(r), the profit or loss for adding r rows of first class seats?

d(r) = 2,200r
d(r) = 5,800r
d(r) = –2,200r
d(r) = –5,800r