Answer:
OK
The component of gravity that aids his sliding down.. is
Mgsin∆
Friction will oppose the motion
Therefore... The net force acting will be
MgSin∆ - Fr=Ma
Where Fr= Frictional Force
Fr = MgSin∆ - Ma
= 20x9.8Sin40 - 20x1.3
=125.99 - 26
=99.99N ~ 100N.