Any challenges that there were in getting the piece/exhibition

Design a pos circuit that displays the letters a through j on a seven-segment indicator. the circuit has four inputs w, x, y, and z which represent the last 4 bits of the uppercase ascii code for the letter to be displayed. thus, if wxyz = 0001 then "a" will be displayed. (any answer with 22 or fewer gates and inverters, not counting any for the inputs, is acceptable)