Subnet Mask: 255.255.240.0
It is a class B network. For a class B network, the upper 16 bits form the network address and lower 16 bits are subnet and host fields.
Of the lower 16 bits most significant 4 bits are 1111. This leaves 12 bits for the host number. So, 4096(212) host address exists.
First and Last address are special so the maximum number of address = 4096 - 2 = 4094.