P = dw/dt
dw = F dot ds
dw = (2i +4j) dot (3j +5k)
   = 12 J
P = 12/2
  P = 6 W
what are you not understand in this step?
how is dot roduct obtained?
Sorry the above statement should have been" How is dot product obtained"??
dot product obtained ; multiply magnitude of two vector and cos(theta) where theta = angle between two vector for above Example 2*3*cos90 = 6*0 = 0 (angle between i and j vector is 90). i hope you will understand if any doubt please ask me.
Thank You Mr.Vikaskumar!!