For each function below, write and evaluate a Riemann sum to calculate $A(f, −2 ≤ x ≤ 1)$ using $24$ left endpoint rectangles.

1. $f(x) = 2^x$

   Hint (a):

   where $a$ and $b$ are the starting and ending values and $n$ is the number of rectangles.

2. $f ( x ) = \sqrt { x + 2 }$

   Hint (b):

   Refer to the hints in part (a).