There are 3 series, you have to find values of a, b and c and then use them to solve the following equation and find the absolute value of k.

50% of b – 14.28% of 7a + c = k

(i) 1221, 1364, 1561, 1816, a, 2540

(ii) 1160, 1329, b, 1979, 2508, 3349, 4310

(iii) 136, 154, 202, 302, 482, c