If the sum of the first 2n terms of the A.P. 2, 5, 8, ...., is equal to the sum of the first n terms of the A.P. 57, 59, 61, ...., then n equals
The sum of first n terms fo an AP is (5n−n2) the nth term of the AP is (a) (5-2n) (b) (6-2n) (c) (2n-5) (d) (2n-6)