A professor has learned th a t th ree stu d en ts in her class of 20 will ch eat on th e exam . She decides to focus her atten tio n on four random ly chosen stu d e n ts during th e exam .

a. W hat is th e probability th a t sh e finds at least o n e of th e stu d e n ts cheating?

b. W hat is th e probability th a t she finds at least o n e of th e stu d en ts cheating if sh e focuses on six random ly chosen students? L05