Answer:
Step-by-step explanation:
Leaving leap years, a year contains 365 days.
For a group of 100 people, each person is independent of the other and probability of any day being his birthday has a chance of

a) Probability that exactly 3 people have same birthday = 
Each day is independent of the other
And hence no of days having exactly 3 persons birthday out of 100 persons is binomial with n = 365 and p = 
Expected value of days = np = 
b) Distinct birthdays is binomail with p =1/365 and n = 365
Hence
expected value = np =1
Answer:
0
Step-by-step explanation:
1-1=0
It's common knowledge that 1-1=0 so I dont know how to explain it any further
Then d = e by transitive property