a body of mass 5kg strikes a body of mass 2.5kg initially at rest which after collision begins to move with K.E. of 5J.assuming the collision to be elastic,then K.E. of first body before impact is:

a 0.62J

b 5.62J

c 7.28J

d 4.20J

don't know the answer guys but this one is simple but i'm not getting any of these 4 answers so plz help me