Chebyshev's Sum Inequality/Discrete/Also presented as

Chebyshev's Sum Inequality (Discrete): Also presented as
Some sources present Chebyshev's sum inequality as:
 * $\ds n \sum_{k \mathop = 1}^n a_k b_k \ge \paren {\sum_{k \mathop = 1}^n a_k} \paren {\sum_{k \mathop = 1}^n b_k}$