[anonymoushn]

I tried solving the version of the problem in which codes are not necessarily unique, the grid an array of 36 squares in which each letter/number contained in any of today's specials has been crossed out, an item "appears" to be available iff all of its letters/numbers have been crossed out, and the customer picks one of the 250 items uniformly at random.

It seems that this is not the correct interpretation of the problem statement.