As shown, a worker pushes a load of 500 N onto a platform with a force of 180 N by using an inclined plank. The 180N force is parallel to the inclined plank. The plank is 3 m long and the platform is 1 m above the ground. a. Find the potential energy gained by the load.

b. Find the work done by the worker.

c. Find the energy wasted during this process.

d. Hence, calculate the frictional force along the plank.