Samantha sends her son, barry, to a preschool center on certain days. the cost of preschool is $45 per day along with a fixed monthly charge of $70. last month, samantha paid a total of $880 to the preschool center. let d represent the number of days barry spent at the preschool center last month. which equation represents this situation, and how many days did barry attend preschool last month? a. 880 = 90d + 45; 9 days b. 880 = 70d - 45; 21 days c. 810 = 45d; 19 days d. 880 = 45d + 70; 18 days