Given
$$F(x, y) = x^2\mathbf{i} + xy\mathbf{j}$$ $$x^2 + y^2 = 49$$
Find the work done by the force field on a particle that moves once around the circle oriented in the clockwise direction.
I've been using $$ \int_C F(\vec{r}(t))\cdot \vec{r}'(t) dt $$ to do other similar problem but usually $\vec{r}$ is given.