Chapter 5, Problem 4P

While two forces act on it, a particle is to move at the constant velocity $\stackrel{\to }{v}\text{ = }\left(\text{3 m/s}\right)\hat{i}-\left(\text{4 m/s}\right)\hat{j}$.One of the forces is ${\stackrel{\to }{F}}_1=\left(2\text{ N}\right)\hat{i}\text{ + }\left(-6\text{ N}\right)\hat{j}$. What is the other force?