i find it hard to understand why you would want to use a nand gate for this?B/C a nand gate is like an or gate,,, if A&B is low then = 1
if A&B is High then = 0
if A or B is high then = 1
the or part just ruins it for this decoder i think.
butt if you have a chip or something you are studying i wouldent ming helping you do a little research.