A block of mass 5 kg is placed on a rough inclined plane. The inclination of the lane is gradually increased till the block just begin to slide down The inclination of the plane is then 3 in 5 The coefficient of friction between the block and the plane is \[\left( \text{g}=\text{ 1}0\text{ m}/{{\text{s}}^{\text{2}}} \right)\]

• A.  3/5 
• B.  3/4 
• C. The upper scale will read 10 kg and the lower scale zero
• D.  2/3