Explanation:
The momentum is defined as the product between the mass and velocity:
p = m·v
Let's calculate his total momentum:
ptot = 70kg · 10m/s = 700 kg·m/s
Now we know that he's traveling 30 degrees south-east.
The momentum along the y axis will be:
py = p·cos30° = 606 kg·m/s
Along the x-axis:
px = psin30° = 350 kg·m/s
D = m /v
d = 30 / 0.5 Kg/m³
d = 60 Kg / m³
In short, Your Answer would be Option A
Hope this helps!