Paragraph: A small block of mass 1 ~kg is released from rest at the...

Paragraph: A small block of mass $1 \mathrm{~kg}$ is released from rest at the top of a rough track. The track is a circular arc of radius $40 \mathrm{~m}$. The block slides along the track without toppling and a frictional force acts on it in the direction opposite to the instantaneous velocity. The work done in overcoming the friction up to the point $Q$, as shown in the figure below, is $150 \mathrm{~J}$. (Take the acceleration due to gravity, $g=10 \mathrm{~m} \mathrm{~s}^{-2}$ ).

Question: The magnitude of the normal reaction that acts on the block at the point $Q$ is