A rod has length 4 meters. At a distance $x$ meters from its left end, the density of the rod is given by $\delta(x)=5 + 2 x$ g/m.

(a) Complete the Riemann sum for the total mass of the rod (use $Dx$ in place of $\Delta x$):
mass = $\Sigma$

(b) Convert the Riemann sum to an integral and find the exact mass.
mass =
(include units)