. To enter the expression 84 , use the syntax 8^4 . To enter the expression C(8, 4), use the syntax comb (8 , 4) . To enter the expression P(8, 4), use the syntax perm (8 , 4) . To enter the expression (8 + 1)!, use the syntax (8 + 1) ! . Remember that any time two terms are multiplied, you must use an asterisk. For example, 8/4 should be written as 8*k^4 (a) Any integer with factorisation 20 . 70 . 11 where a, b, c E N, is said to be 12-regular if and only if it satisfies the condition atb+c=12. How many 12-regular numbers are there? comb(14,2) (b) Suppose x, y E Z. We shall write a ~ y, or say that a is equivalent to y, if and only if x = y x (308)" for some n E Z. Let S be the set of 12-regular integers such that no two elements of this set are equivalent to each other. Then S can be written as S =