One week, Isabelle bought 2 bags of apples and 3 bags of oranges. The next week, she bought 1 bag of apples and 2 bags of oranges. If a represents the cost of each bag of apples and r represents the cost of each bag of oranges, which expression could Isabelle use to calculate the difference between the amounts she spent each week?
3 a minus r
3 a minus 5 r
(2 a minus 3 r) minus (a minus 2 r)
(2 a + 3 r) minus (a + 2 r)