The principal of a high school needs to plan seating for commencement. The following two-way table displays data for the student

s who are involved in this year's commencement ceremony. Grade level In choir Not in choir TOTAL
Junior 15 3 18
Senior 23 436 459
Other 3 0 3
TOTAL 41 439 480
For these students, are the events "senior" and "not in choir" mutually exclusive?
Find the probability that a randomly selected student from this group is a senior OR is not in choir.