Use counting to determine the whole number that corresponds to the cardinality of these sets.
(a) a = {x|x ∈ n and 17 < x ≤ 23},
(b) b = {x|x ∈ n and x − 5 = x},
(c) c = {x|x ∈ n and (x − 88) (x −22) = 0} ,
(d) d = {x|x ∈ n, 1 ≤ x ≤ 100 and x is divisible by both 77 and 22}
n(A)=