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.

The refresher course will start with which one of the following subjects ?