Consider the following three sequences:
A: 3, 6, 9, 12, 15
B: 10, 7, 4, 1, −2
C: 1, 2, 4, 7, 11
a. (i) For each sequence, state with reasons whether it is an arithmetic progression.
b. (ii) For every sequence that is an arithmetic progression, find its common difference.
c. (iii) For every arithmetic progression identified, write the next three terms.