A training college has to conduct a refresher course for teachers of seven different subjects -- Mechanics, Psychology, Philosophy, Sociology, Economics, Science and Engineering from 22nd July to 29th July.
  1. Course should start with Psychology.
  2. 23rd July, being Sunday, should be holiday.
  3. Science subject should be on the previous day of the Engineering subjects.
  4. Course should end with Mechanics subject.
  5. Philosopy should be immediately after the holiday.
  6. There should be a gap of one day between Economics and Engineering.
Which subject will be on Tuesday ?

Answer: C. Economics

The course starts with Psychology. So, Psychology will be on the 22nd, 23rd being a Sunday will be a holiday. Science will be before Engineering and Economics, Science and Engineering. Mechanics will be the last i.e., on 29th. So, Sociology will fill the gap on the 28th.
Thus, we have :

22nd 23rd 24th 25th 26th 27th 28th 29th
Psychology Sunday Philosophy Economics Science Engineering Sociology Mechanics

So, Economics will be on Tuesday, the 25th.