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
 [tex]W = \mu_k m g sin \theta \times d[/tex]
 [tex]W =0.436 \times 4.1 \times 9.8 \times  sin 30^0 \times 2.1[/tex]
 [tex]W =19.39\ J[/tex]
b) Work done due to friction = [tex]\mu N L[/tex]
               =  [tex]-\mu m g cos \theta L[/tex]
               =  [tex]-0.436 \times 4.1 \times 9.8 \times cos 30^0 \times 2.1 [/tex]
               = -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
