1.6: AP sum threshold and GP sum to infinity

An arithmetic progression has a second term of 8 and a fourth term of 18. Find the least number of terms for which the sum of this progression is greater than 1560.

A geometric progression has a sum to infinity of 72. The sum of the first 3 terms of this progression is $\tfrac{333}{8}$.

Find the value of the common ratio.

Hence find the value of the first term.