Porocedure-1:
Network address=IP address && Network Mask (and operation in binary equivalent).
Procedure-2:
Mask:255.255.224.0 So third octet having 3 bits netid and 5 bits host id
So block size is(2^5) i.e. 0,32,64,96,128......so on
By looking to the ip addres125.134.112.66, third octet 112 comes under 96 subnet. Hence Ans.