For a certain arithmetic progression the sum of the first n terms is given by Sn=3n2+5n for every natural number n.
a. (i) Express the nth term Tn of the progression in terms of the sums Sn and Sn−1.
b. (ii) Using the relation found in part (i), write down the first three terms of the progression.
c. (iii) Hence find the first term and the common difference of the progression.