Mr. and Mrs. Miller both get in their cars and begin to drive at the same time. Mr. Miller is 280 mi from their house and drives directly home at a constant rate of 40 mph. Mrs. Miller is at their house and drives away from the house at a constant rate of 30 mph.

Let d represent distance from home, and let t represent time in hours.

Which system models this situation?

a. d = 280 + 40t

d = 30t

b. d = 280 - 30t

d = 40t

c. d = 280 - 40t

d = 30t

d. d = 280 - 40t

d = 280 + 30t