You're most welcome Camilo!

Hello Camilo,

If your English level is intermediate and above, I suggest starting with Mastering skills for ibt. This book has audio files for its reading passages too which means after answering the reading questions you can listen to them. After this book, I would work on Barron's and Oxford books for TOEFL. 

Hope this helps,

Ameneh

Duh! How come you don't know what an integal is?!!!!! Just kidding. I'm glad to see someone here does not care about math at all:D 

I agree that his question was irrelevant to your background and the job you had applied for. But asks you a question you don't know the answer, do not lose your confidence and give him an answer showing you abilities. For examples, you might say, I do not have the answer on top of my head right now, and it was not mentioned in the job requirements in your ad either. However, if you think knowing this (say integral, calculus, etc) is required for this position, I can learn it in a week or so. Sometimes the intention is not just receiving a correct answer, but to see how you would react when you don't know the answer. 

About your this experience, to be honest with you, I wouldnt waste my time on someone who belittles people. Even if they had offered you the job you would have hard time working with/for him.

Good luck,

Ameneh