5. An geometric sequence contains the following terms: a5 = 162 and a10 = 39366. Find the sum of the first 8 terms of this sequence. 6. [4 marks] In an arithmetic sequence, the sum of the 3rd and 8th terms is 1. Given that the sum of the first seven terms is 35, determine the first term and the common difference. 7. [4 marks] In an arithmetic sequence, u₁ = 1.3, u₂ = 1.4 and uk = 31.2. a. Find the value of k. b. [2 marks] Find the exact value of Sk. c. [5 marks] Consider the terms, un, of this sequence such that n ≤ k. Let F be the sum of the terms for which n is not a multiple of 3. Show that F = 3240