In a runoff election, if no candidate receives a majority of votes in the first round of

Question:

In a runoff election, if no candidate receives a majority of votes in the first round of voting, the top two candidates face each other in a second round. Let’s say that people voting on Candidates A, B, C, and D in a runoff election have the following preferences. 12 voters: A > B > C > D
8 voters: C > B > D > A
10 voters: D > B > C > A
4 voters: B > D > A > C
a. Does anyone receive an outright majority in the first round? If so, which candidate? If not, which two candidates move on to the second round, and which of them wins?
b. Suppose Candidate A drops out of the race. Does any candidate now receive an outright majority in the first round? If so, which candidate? If not, which two candidates move on to the second round, and which of them wins?
c. Does this situation violate the independence of irrelevant alternatives?