Puzzle #225: Textbooks

You are taking five courses, one each in Accounting, Biology, Computing Science, English, and Japanese.

The cost of the Japanese textbook is twice that of the English textbook. The cost of the Computing Science textbook is twice that of the Accounting textbook. It is also four-thirds of the cost of the Japanese textbook. The Chemistry textbook cost ten dollars more than the average cost of the other four textbooks.

If each textbook cost an exact number of dollars and you spent somewhere in the $300’s, how much did each textbook cost, and what is the total?

Submit your answer to Gene Wirchenko <genew@telus.net>. Your answer should be in the form of a proof. That means to show how your answer must be correct. The deadline is Wednesday, September 27, 2017 at noon Pacific Time. I will post the answer shortly after.