Consider the area between the graph of $f(x)=\sqrt{x}$ and the $x$ -axis on $[0,4]$.
(a) Use the four rectangles shown on the left to approximate the given area, and then use the eight rectangles shown on the right to obtain another approximation of that area. Be sure to use the fact that the graph shown is that of the function $f(x)=\sqrt{x}$ in your calculations.
(b) Describe what would happen if we did similar approximations with more and more rectangles, and make a guess for the resulting limit.