$(11)$ An $8\mathrm{.}0-kg$ block is released from rest, with $v_1=0\frac{m}{s},$ on a rough incline, as shown in the figure. The block moves a distance of $1\mathrm{.}6-m$ down the incline, in a time interval of $0\mathrm{.}80$ s $,$ and acquires a velocity of $v_2=4\mathrm{.}0\frac{m}{s}.$ How much work does gravity do on the block during this process?

A$.+81$ J

B$.+100$ J

C$.+120$ J

D$.-81$ J

E$.-100$ J

$N=mg$