The value of $6\left[\cos 50^{\circ}+\mathrm{i} \sin 50^{\circ}\right] \div 3\left(\cos 20^{\circ}+\mathrm{i} \sin 20^{\circ}\right)$ in polar form is
(a) $2\left(\cos 30^{\circ}+\mathrm{i} \sin 30^{\circ}\right)$
(b) $5\left(\cos 30^{\circ}+i \sin 30^{\circ}\right)$
(c) $2\left(\cos 30^{\circ}-\mathrm{i} \sin 30^{\circ}\right)$
(d) $3\left(\cos 70^{\circ}+i \sin 70^{\circ}\right)$