hey i am using the normal reaction offered by the floor on the chain which is equal to the force exerted by the chain on the floor

N=N_wt+N_thrust

N_wt=(m/l)xg

N_thrust=V_relative(dm/dt)

V_relative=u-v = v

dm/dt=(dm/dy)(dy/dt)=m/l(v)

N_thrust=v²(m/l)

v=(2gx)^1/2

N_thrust=2gx(m/l)

N=(m/l)gx+2gx(m/l)=3(m/l)gx