An object of mass 2kg moving with a velocity 3ms^-11 collides head-on with another object of mass 1kg moving in the opposite direction with a velocity of 4ms^-1. If the objects stick together after collision, calculate their common speed.

• A.0.60ms^-1
• B.0.67ms^-1
• C.2.00ms^-1
• D.3.33^-1