40. Tickets for the Senior Talent Show at George Washing- ton Carver High School are $3 for adults and $2 for students. To cover expenses, a total of $600 must be collected from ticket sales for the show. One of the fol- lowing graphs in the standard (x,y) coordinate plane, where x is the number of adult tickets sold and y is the number of student tickets sold, represents all the poss- ible combinations of ticket sales that cover at least $600 in expenses. Which graph is it?