A small, plastic sphere of mass $m=100 \mathrm{g}$ is attached to a string as shown in Figure $\mathrm{P} 17.45$ There is an electric field of $100 \mathrm{N} / \mathrm{C}$ directed along the $+x$ direction. If the string makes an angle $\theta=30^{\circ}$ with the $y$ axis, what is the charge on the sphere?