Suppose that the density of cars (in cars per mile) down a 20-mile stretch of the Pennsylvania Turnpike is approximated by $\delta(x) = 250 \left(2+\sin\left(4\sqrt{x + 0.125}\right)\right),$ at a distance $x$ miles from the Breezewood toll plaza. Sketch a graph of this function for $0\leq x\leq 20$.

(a) Complete the Riemann sum that approximates the total number of cars on this 20-mile stretch (use $Dx$ instead of $\Delta x$):
Number = $\Sigma$

(b) Find the total number of cars on the 20-mile stretch.
Number =