$(1$ point$)$

The rectangles in the graph below illustrate a left endpoint Riemann sum for $f(x)=\frac{x^2}{12}$ on the interval $4,8.$

The value of this left endpoint Riemann sum is $,$ and this Riemann sum is an underestimate of the area of the region enclosed by $y=f(x),$ the $x-$axis, and the vertical lines $x=4$ and $x=8.$