Speed reduction in a gear box is achieved using a worm and worm wheel. The worm wheel has 30 teeth and a pitch diameter of \(210 \mathrm{~mm}\). If the pressure angle of the worm is \(20^{\circ}\), what is the axial pitch of the worm?

(a) \(7 \mathrm{~mm}\)

(b) \(22 \mathrm{~mm}\)

(c) \(14 \mathrm{~mm}\)

(d) \(63 \mathrm{~mm}\).