Consider the following for the next items that follow:

Let a1, a2, a3 ... be in AP such that a1 + a5 + a10 + a15 + a20 + a25 + a30 + a34 = 300.

What is $\displaystyle \sum_{n=1}^{34} a_n$ equal to ?

If log_xa, a^x and log_bx are in GP, then what is x equal to ? 

If $2^{\frac{1}{c}}, 2^{\frac{b}{a c}}, 2^{\frac{1}{a}}$ are in GP, then which one of the following is correct ? 

The first and the second terms of an AP are $\frac{5}{2}$ and $\frac{23}{12}$ respectively. If n^th term is the largest negative term, what is the value of n ?