Suppose $\vec{F}(x,y,z) = -y\vec{i} + x\vec{j} + 0.5\vec{k}$ and $C$ is the helix given by $x(t) = 4 \cos(t)$, $y(t) = 4 \sin(t)$, $z(t) = t/4$ for $0 \leq t \leq 3 \pi$. (a) From the graph, do you expect the line integral of $\vec{F}$ along the helix $C$ to be positive, negative, or zero? ? positive negative zero (b) Find the line integral of $\vec{F}$ along the helix $C$. $\displaystyle \int_C \vec{F} \cdot d\vec{r}$ =