The efficiency of an inclined plane is 70%. What is its length if a force of 60N is required to lift

The efficiency of an inclined plane is 70%. What is its length if a force of 60N is required to lift a load weighing 28 kg? The height of the inclined plane is 60 cm.

Step one.
Let us determine what useful work will be done if, according to the condition of this task, the mass of the load lifted to a height of 60 centimeters is 28 kilograms:
60 cm is 0.6 kg;
Apol = m * g * h;
28 * 10 * 0.6 = 168.
Step two.
Now we need to determine what work was actually expended to lift this load:
Azatr = Apol: efficiency * 100%;
168: 70 * 100 = 240.
Step three.
Find out what the length will be:
Azatr = F * l;
240: 60 = 4.
Answer: 4 meters.