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C2 Help - Geometric Series

I'm using the Edexcel Heinemann textbook, and doing exercise 7F, question 6. I showed that the common ratio was 0.4, but my other answers don't agree with the back of the book.
For part b) i got 2000 rather than 200 by dividing 80 by 0.04. I then got 2083.333 for the sum to infinity which is apparantly completely wrong. Can anyone help me out?

Post the question?

The second term of a geometric series is 80 and the fifth term of the series is 5.12
a)Show that the common ratio of the series is 0.4
Calculate:
b) the first term of the series
c) the sum to infinity of the series, giving your answer as an exact fraction
d) the difference between the sum to infinity of the series and the sum of the first 14 terms of the series, giving your answer in the form of a x 10^n, where 1<a<10 and n is an integer.

Thankyou in advance!!!

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