A change order submitted by main contractor requesting time extention together with extra cost. How to decide if he can claim or not?

Evaluate his request with agreed terms and conditions of contract. If it is genuine case of delay, for reasons beyond control of contractor you may accept time extension. However, this will also depend on if this delay affected your company business and  what kind of relations your company is willing to maintain with this contractor for future projects. Matter of extra cost should be negotiated and may or may not be accepted in full or partial.

AGREE WITH THE ANSWER GIVEN BY

Mr: KHEDKAR