How much KE is lost during the collision?$$

$12$Mm$+$Mv$2012$Mm$+$Mv$0212$mMm$+$Mv$2012$mMm$+$Mv$020($Energy is conserved in this collision$\mathrm{.}12$mv$2012$mv$02$ All kinetic energy is lost$12$mMM$$mv$2012$mMM$$mv$02$