Refer to the following number series and answer the question that follows. Counting is to be done from left to right only. (All numbers are single-digit numbers.) (Left) 8 4 2 5 9 4 3 5 1 4 6 7 2 1 7 6 7 9 5 4 1 3 6 2 9 7 6 7 9 5 (Right) How many such even digits are there, each of which is immediately preceded by an even digit and also immediately followed by an even digit?

Refer to the following number series and answer the question that follows (all numbers are single-digit numbers only). Counting is to be done from left to right only. (Left) 7 1 4 3 6 2 7 9 6 5 1 1 7 7 3 2 5 5 3 6 6 5 6 2 1 9 1 (Right) How many such odd numbers are there, each of which is immediately preceded by an odd number and also immediately followed by an odd number?

There are 7 friends F1, F2, F3, F4, F5, F6, and F7 with two-digit consecutive roll numbers such that all of them are composite numbers and there is no prime roll number in between them. What is F2's roll number if none of the numbers exceed 100 and the friends are ordered by roll number in ascending order?