Scenario 1-1 Suppose a T-Shirt Manufacturer Currently Sells 5,000 T-Shirts Per Week

Scenario 1-1
Suppose a t-shirt manufacturer currently sells 5,000 t-shirts per week and makes a profit of $10,000 per week.A manager at the plant observes,"Although the last 400 t-shirts we produced and sold increased our revenue by $4,000 and our costs by $4,800,we are still making an overall profit of $10,000 per week so I think we're on the right track.We are producing the optimal number of t-shirts."
-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 400 t-shirts?

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