In: Advanced Math
One of the statements below is true, and the other is false. Identify which is which, give a direct proof of the true one, and give a counterexample to the false one.
(a) The sum of every four consecutive integers is a multiple of 4;
(b) the sum of every five consecutive integers is a multiple of 5.
(An arbitrary set of four consecutive integers can be written as n, n + 1, n + 2, and n + 3 for some n ∈ Z.)