Answer:
1. 218.55 N
2. 
3. 
Explanation:
Part 1;
Net force
where m is mass, g is gravitational force and
is the angle of inclination

Frictional force,
is given by
where
is the coefficient of static friction


Since
, therefore, the block doesn’t slip and the frictional force acting is mgh=218.55N
Part 2.
Using the relationship that
Frictional force 



The maximum angle of inclination 

Part 3:
Net force on the object is given by
where
is the coefficient of kinetic friction

= 9.8 ( sin 38 - (0.51) cos 38 )
= 
Force of friction=75 N
Explanation:
we use Newton's second law of motion
F- Ff= ma
F = applied force=250 N
Ff= force of friction
a= acceleration= 5.83 m/s²
m= mass=30 kg
250- Ff= 30 (5.83)
Ff=250-30(5.83)
Ff=250-175
Ff=75 N