Consider an AP with first term 2 and common difference 5, and a GP with first term 2 and positive common ratio r.
a. (i) If the sums of the first 4 terms of the two progressions are equal, find the value of r.
b. (ii) For the value of r obtained in part (i), determine which of the two sums is larger when n≥5. Give a clear justification.