Answer
mass of the block = 4.10 Kg
distance of slide = 2.1 m
angle of inclination = 30.0°
μ_k be equal to 0.436
a) Work done by the gravity



b) Work done due to friction = 
= 
= 
= -31.86 J
c) work done by the normal force = 0 J
Since normal force and displacement are perpendicular to each other
d) for steeper angle
sin θ value is high
cos θ value is less
work done by gravity on steeper angle is more
work done by frictional force will on steeper angle is less
work done by normal force is zero