On July 10, Boogie Footware agrees to a contract to sell 800 pair of flapper shoes for $16,000 to Twenties, Inc. On September 1, after 500 pair have been delivered, Boogie and Twenties modify the agreement to reduce the price of the remaining 300 pair of flapper shoes to $10 a pair. During Sept, Boogie delivers 200 pairs of shoes. How much revenue will Boogie recognize for the month of September?

I know the answer is $1,375 but I need to see the work for this problem.