My Dear Friend,
You can get the answer for this question from the same Mathur Sharma Book and also in Automobile technology by Author Kripal Singh Book too..
In ur mail you have stated that "we all students need official reply not from any student who has just attempted the exam."
But pls be noted that , This discussion forum is for discussing all aspects of all academic programmes on offer from this university; All students (prospective and enrolled) and counselors at all study centers are welcome here to interact with each other and with the university staff for ENHANCING / SHARING THE KNOWELEDGE.
Hence , just to make the students to know from where they can get the answer, I wrote it is available in the same book; Nothing else..; As said by you, if university is going to provide 5 marks to us, I too will get benifit in this..
Rgds,
Ganesh