I don't know how to figure this out, partially think I studied the wrong chapter

Question 11 The average age of doctors in a certain hospital is 420 years old with a standard deviation of 10D years, If 16 dudors are chosen at random fur a committee nd the probability that the mean age of those doclnrs is less Ihan 4350 years. Assume that lire variable is normally distributed, 0 0.7757 0 0.2743 0 :15757 0 0.6857 Question 12 In a certain college, 33% of the thsic majors belong in ethnic minuritis. Find lire probability that. from a random sample of 10 phi/sic majors, exactly 4 do not belong to an ethnic minority. 0 0.2753 0 aura 0 mm! 0 {12564 Question 15 A computer company ships an order of [our computers. The following table gives the probability distribution for the number X of defective computers in the shipment )1: El 1 2 3 It F'Dill: 0.452 0.39? H.131 0.015 0.005 ai Find the mean of the distribution. b] Find the standard deviation of the distribution