The figure shows the velocity of an object for $0t8.$ Calculate the following estimates of the distance the object travels between $t=0$ and $t=8.$ Indicate whether each is an upper or lower estimate of the distance traveled.

$($a$)$ The left sum with $n=2$ subdivisions is and it is

$($b$)$ The right sum with $n=2$ subdivisions is lours$)$ and it is