21 The numbers 2, 3, 3, 4, 4, 4 are written on six cards. Two cards are chosen, at random, without replacement, to form a 2-digit number. The first card chosen shows the number of Tens. The second card chosen shows the number of Units. Expressing each answer in its simplest form, find the probability that the two cards show (a) a number greater than 20, (b) the number 33, (c) the number 43 or the number 32.