72% of all students at a college still need to take another math class. If 36 students are randomly selected, find the probability that

a. Exactly 25 of them need to take another math class.-------------

b. At most 28 of them need to take another math class.------------

c. At least 27 of them need to take another math class.--------------

d. Between 23 and 31 (including 23 and 31) of them need to take another math class-------------