Please show me the solution for: A company sold 4000 gallons of milk in jars to Mr. Marcellus' store at the cost of $3.5 per gallon. However, Mr. Marcellus later realized 2/5 of the amount of milk he purchased had passed the expiry date and could not be sold. He returned the sour milk to the company and ordered a refund. Calculate how much he got in refunds.