If $z_{1}=10(\cos 100^{\circ}+i \sin 100^{\circ})$ and $z_{2}=5(\cos 40^{\circ}+i \sin 40^{\circ})$, then find the following in polar form: (a) $z_{1} \cdot z_{2}$, (b)

$$\frac{z_{1}}{z_{2}}\text{.}$$