Final answer:
The adjusted income from installment sales for 2018 cannot be determined based on the given information.
Step-by-step explanation:
The adjusted income from installment sales for 2018 can be determined by subtracting the total amount of cost of goods sold and operating expenses from the total revenue generated from installment sales. To calculate the adjusted income, you need detailed financial information that is not provided in the question. Without that information, it is not possible to determine the adjusted income for 2018. Therefore, we cannot choose any of the options given (a, b, c, or d) as the correct answer.