10nnnnnn

If the first byte (8 bits) of an address is a class B address, it will have 10 in the first 2 bits. Since this 8 bit number is a binary number, each of the next 6 bits would be a 1 or a 0. That means the largest possible binary number for that first byte would be 10111111 or 191 in decimal (128+0+32+16+8+4+2+1). The smallest possible binary number for that first byte would be 10000000 or 128 in decimal (128+0+0+0+0+0+0+0).