Mary owns a small business. she spent $4,500 to get the business started. she has noticed that her monthly operating costs have been consistent. after five months, she has spent a total of $5,250 in start-up costs and monthly operating costs. in a linear model of this situation, which of the following statements applies? a. an additional month of business operation is associated with an additional $50 in costs. b. an additional month of business operation is associated with an additional $150 in costs. c. an additional month of business operation is associated with an additional $750 in costs. d. an additional month of business operation is associated with an additional $500 in costs.