A steel block of 10 kg rests on a horizontal floor as shown. When three iron cylinders are placed on it as shown, the block and cylinders go down with an acceleration 0.2 m s$$^{-2}$$. The normal reaction $$R'$$ by the floor if mass of the iron cylinders are equal and of 20 kg each is (in N),   [Take $$g = 10$$ m s$$^{-2}$$ and $$\mu_s = 0.2$$]

A

716

B

686

C

714

D

684