There are multiple paths to solve this problem, but we will go with the most straight forward. There are two forces acting on the sledder in the direction of their motion: kinetic friction and a component of the gravitational force. The problem statement tells us that the sledder is traveling a constant velocity, so we know that these forces are equal and opposite. Therefore we can calculate the component of gravitational force and set that equal to the frictional force. We can then use that and the sledder's velocity to calculate power. So to begin, the force of gravity:

However, this is a vertical force and we need the component that is in the direction of the sledder. Therefore, we will multiply by sin:

If you're wondering why sin was used, think about the situation practically. As the angle grows, the hill gets steeper, and there will be more gravitational force in the direction of acceleration. Sine is the function that gets larger as the angle gets larger.

We can now set this equal to the frictional force:

Plugging in values for this:

Now to get the power that this force uses, we can multiply it be the velocity that it is applied at. If this is confusing, take it in steps. If we multiple a force by distance, we get energy. If we multiple energy by frequency, we get power. And distance times frequency is simply velocity. Moving on:

By definition, 

Because the box is moving at constant velocity, we know that the work done by the forklift must be equal to the work done by gravity, written as:

Combining this with the time we would like to raise the box, we can calculate the power,

Power in general is written as 

In this form, the problem is not able to be solved.  However, if we think a bit outside of the box, we can massage the expression for power in such a way to solve our problem.  Consider

Using our altered definition of power, we can calculate: 

All energy is kinetic, and the initial energy is zero, so:

Combining equations:

Converting minutes to seconds and plugging in values:

To have power, an object needs to have a force and a velocity:

The acceleration comes from the air resistance that's trying to constantly decelerate the cyclist, and the velocity is the speed the cyclist is maintaining:

Using

Using

and

All energy will be kinetic. Combining equations:

Plugging in values:

Using

Determining initial kinetic energy:

Combining equations

Converting to and plugging in values:

Determining final kinetic energy:

Combining equations

Converting to and plugging in values:

Plugging in values:

Using

The expression for gravitational potential energy is:

And power is:

Therefore, we get:

Plugging in our values, we get:

The work will be equal to the gravitational energy change:

Using

In this question, we're given a few different variables. We're told there is energy, time, displacement, force, and mass involved. So, we need to think about a way to relate these all together, given what the question is asking.

We're told that energy is being transferred to an object at a certain rate. This energy transfer results in a force on the object which, in turn, causes it to undergo displacement. Finally, we know the mass of the object as well.

Since we're told that the energy is being transferred at a certain rate, we know power is involved. We also know that the change in energy of an object is equal to the force that object experience multiplied by its distance. Thus, we can relate these variables with the following expression.

Using this expression, we can rearrange it in order to isolate the term for time.

Now, we just need to plug the values given in the question stem to solve for our answer.

Also notice that we didn't need to use the object's mass to solve this problem. That was extraneous information.