A sequence of 4 digits, when considered as a number in base 10 is four times the number it represents in base 6. What is the sum of the digits of the sequence?

PAIN:SEDATIVE

There are n terms in an arithmetic progression. The n terms of the arithmetic progression are now distributed into eight sub-series - S1, S2and S8 - as follows. The 1st, 9th, 17th terms and so on go into S1; the 2nd, 10th, 18th terms and so on go into S2; the 3st, 11th, 19th terms and so on go into S3, and so on for S4 till S8. If for exactly three of the eight sub-series, the average of the sub-series is a term of the same sub-series, which of the following could be a possible value of n?