Over a long period of time in a large multinational corporat

Over a long period of time in a large multinational corporation, 15% of all sales trainees are rated as outstanding, 75% are rated as excellent/good, 6% are rated as satisfactory, and 4% are considered unsatisfactory. Compute the probability that three out of the 10 trainees are rated as satisfactory or excellent/good.   

Solution

probability that three out of the 10 trainees are rated as satisfactory or excellent/good = (10C3)*(0.81^3)*0.19^7 = 0.00057