Scenario 1-1 Suppose a Cell Phone Manufacturer Currently Sells 20,000 Cell Phones

Scenario 1-1
Suppose a cell phone manufacturer currently sells 20,000 cell phones per week and makes a profit of $5,000 per week. A manager at the plant observes, "Although the last 3,000 cell phones we produced and sold increased our revenue by $6,000 and our costs by $6,700, we are still making an overall profit of $5,000 per week so I think we're on the right track. We are producing the optimal number of cell phones."
-Refer to Scenario 1-1.Using marginal analysis terminology, what is another economic term for the incremental revenue received from the sale of the last 3,000 cell phones?

A) gross earnings
B) marginal revenue
C) sales revenue
D) gross profit