On a hospital staff, there are 4 dermatologists, 7 surgeons, 5 general practitioners, 3 psychiatrists, and 3

Question:

On a hospital staff, there are 4 dermatologists, 7 surgeons, 5 general practitioners, 3 psychiatrists, and 3 orthopedic specialists. If a doctor is selected at random, find the probability that the doctor is
a. A psychiatrist, surgeon, or dermatologist
b. A general practitioner or surgeon
c. An orthopedic specialist, a surgeon, or a dermatologist
d. A surgeon or dermatologist