Of the students living in the dormitories at aa€‹ university, 65% live at the westa€‹ hall, and the rest at the south tower. A sandwich shop randomly mails a coupon for a free sandwich to 24% of those at the westa€‹ hall, and to 19% of those living at the south tower. Let D be the event that the person receive a coupon, E1 be the event that the person is living in the westa€‹ hall, and E2 be the event that the person is living in the south tower. A student living in a dormitory is randomly chosen. Required:
Find the probability that this person received a coupon. Also write an expression that models the probability.