Assume There Are Three Hardware Stores, Each Willing to Sell

Assume there are three hardware stores, each willing to sell one standard model hammer in a given time period. House Depot could offer a hammer for a minimum of $7. Lace Hardware could offer a hammer for a minimum of $10. Bob's Hardware could offer a hammer for a minimum of $13.If the market price of hammers increased from $9 to $13, producer surplus would:

A) increase for each producer.
B) increase only for House Depot.
C) remain unchanged for Bob's Hardware.
D) increase by $4 for Lace Hardware.