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 $0.2 \mathrm{~m} / \mathrm{s}^2$. The normal reaction R' by the floor if mass of the iron cylinders are equal and of 20 kg each, is ______ N.
[Take $g=10 \mathrm{~m} / \mathrm{s}^2$ and $\mu_2=0.2$ ]