Correct option is A
Given:
AMBER is coded as 36, MAGENTA is coded as 57

Logic: Sum of all alphabetic position – number of consonant in the alphabet
AMBER:
A = 1, M = 13, B = 2, E = 5, R = 18
Sum = 1 + 13 + 2 + 5 + 18 = 39
Now, 39 – 3 = 36
MAGENTA:
M = 13, A = 1, G = 7, E = 5, N = 14, T = 20, A = 1
Sum = 13 + 1 + 7 + 5 + 14 + 20 + 1 = 61
Now, 61 – 4 = 57
PURPLE:
P = 16, U = 21, R = 18, P = 16, L = 12, E = 5
Sum = 16 + 21 + 18 + 16 + 12 + 5 = 88
Now according to the logic 88 – 4 = 84
Thus, correct option is (a).