Match each of the set on the left described in the roster form with the same set on the right described in the set-builder form :
(i) {P, R, I, N, C, A, L} (a) { x : x is a positive integer and is a divisor of 18}
(ii) { 0 } (b) { x : x is an integer and `x^(2) – 9 = 0`}
(iii) {1, 2, 3, 6, 9, 18} (c) {x : x is an integer and `x + 1= 1`}
(iv) `{3, –3}` (d) {x : x is a letter of the word PRINCIPAL}