[Maximum mark: 6] Only one of the following four sequences is arithmetic and only one of them is geometric. an = 1, 5, 10, 15, ... Cn = 1.5, 3, 4.5, 6, ... on = 1 2 3 4 1 1 2'3'4' 5'... dn = 2, 1, 2' 4' . . (a) State which sequence is arithmetic and find the common difference of the sequence. [2] (b) State which sequence is geometric and find the common ratio of the sequence. [2] (c) For the geometric sequence find the exact value of the eighth term. Give your answer as a fraction. [2] [Maximum mark: 6] The help An arithmetic sequence has u1 = 40, u2 = 32, us = 24. (a) Find the common difference, d. [2] (b) Find us. [2] (c) Find Sg. [2]