A Trader Frauds By 10% While Buying And 10% While Selling The Same . What Is The Total Gain He Obtained In The Transcation?

A) 13 B)22.25 C) 20 D) None Of These

I Approached In The Following Way

First I Tought The Selling Price As X

And Our Fraud Seller Will Get That For 90x/100 = .9x

And Now Our Seller Will Sell That With A Gain Of 10%

So Selling Price Now Is 110/100(.9x) = 9.9x

Then Im Not Understanding What To Do ???