Joey's Lawn cutting Service rents office space from Joey's dad for $300 per month. Joey's dad is thinking of increasing the rent to $400 per month (but will not change the cost of mowing an additional lawn). As a result, after the rent hike, Joey's marginal cost of cutting grass will a. increase by $100 divided by the amount of grass cut. b. increase by $100. c. decrease by $100. d. not change.