It is required to cut screw threads of 2 mm pitch on a lathe. The lead screw has a pitch of 6 mm. If the spindle speed is 60 r.p.m., then the speed of lead screw will be

• 10 r.p.m.
• 20 r.p.m.
• 120 r.p.m.
• 180 r.p.m.