Molly and Tess like to shop at the mall. Their sister Jessica prefers to play bocce ball instead. Molly has $280 in her bank account and spends $40 on every trip to the mall. Tess has $170 in her account and spends half as much as Molly during each trip. Jessica has $50 in her account and does not spend any of it. a. How many trips to the mall will it take for the Molly and Tess to have the same amount of money in their accounts? Show all of your work and explain your method for calculating the number of trips. HINT: Make some equations

b. When will Jessica have the largest bank account? How do you know?