Let the sums of the first p and first q terms of an arithmetic progression be equal, where p<q.
(i) Establish the relationship between p, q and the common difference d that is implied by the condition Sp=Sq.
(ii) Prove that the sum of the next (q−p) terms is zero.
(iii) If p=5 and q=8, find the first term of the AP in terms of d, and hence obtain its numerical value when d=3.