Hello! Please show how to solve this question! I don't know how to solve the second part of the question...

In a geometric progression, the first term is 12, and the fourth term is (-3/2).

i)Find the sum of the first n terms of the progression,Sn.

ii) Find the sum to infinity,S,of the progression[I found this to be 8]and the least value of n for which the magnitude of the difference betweenSnandSis less than 0.001.

Thank you very much!!