$${\begin{align*} J_y &= m(v_{fy} - v_{iy}) \\&= \mathrm{(80 \, kg) [(50 \, m/s) \sin (-10^\circ) - (70\, m/s) \sin 30^\circ]} \\&= -3495\, \mathrm{kg \cdot m/s} \approx -3000\, \mathrm{kg \cdot m/s}\end{align*}}$$