yupp. actually after commenting here, i again tried on google to find and i got that. after that i tried to delete this comment also but it continuousy showed database error and denied me to delete. but any way thanks for concern. anyway how to tag people in comment? i tried here but i failed.
i think question is a bit wrong. it should be "subnet id" not "subnet mask". bcz, in subnet mask all subnet bits are marked 1 and calculated. so as here odd position bits are 1, so during calculating subnet mask, we put all 1/s upto last but 1. so subnet mask should be 255.255.255.254. yes as one of the subnet id 255.255.170.170 is ok. bcz host id bits and network id bits can never be inter leaved. #solve doubt @pritamprasun sir.