Solve the Problem $S$ , of the First $n$ Positive Integers Is Given by the Following Formula

Multiple Choice

Solve the problem.
-The sum, $S$ , of the first $n$ positive integers is given by the following formula: $S=\frac{n(n+1) }{2}$ . What is the sum of the first 27 positive integers?

A) 378
B) 14
C) 28
D) 189