Correct Answer: 66

Solution : Given:
PHONE is coded as 78 and MOON is coded as 52.

Add 1 in the sum of the position values of opposite letters of PHONE, to obtain the required code –
Opposite letter pairs for PHONE –
P – K – 11; H – S – 19; O – L – 12; N – M – 13; E – V – 22
(11 + 19 + 12 + 13 + 22) + 1 = 78
Thus, PHONE is coded as 78.
And in, MOON is coded as 52 –
M – N – 14; O – L – 12; O – L – 12; N – M – 13
(14 + 12 + 12 + 13) + 1 = 52
Thus, MOON is coded as 52.
Similarly, by following the same pattern for PLAN –
P – K – 11; L – O – 15; A – Z – 26; N – M – 13
(11 + 15 + 26 + 13) + 1 = 66

Thus, PLAN is coded as 66. Hence, the fourth option is correct.