Lisa buys a dozen apples and two oranges. Jeremy buys six apples. Oranges cost $1 each, and they spent $9 total. Which of the following shows how to define the variable in order to find the cost of the apples and oranges? A. cost of apples − a cost of oranges − O B. a + cost of apples O + cost of oranges C. a − cost of apples O − cost of oranges D. a = cost of apples O = cost of oranges