The correct answer is (a.) The rider uses energy to do work going up the mountain. As the law of conservation of energy states that the total energy must be constant, therefore, the energy that is used to go up will be as it is to go down.
Answer:
a)
b)
.
Explanation:
Given that
Boyle's law
P V = Constant ,at constant temperature
a)
Given that


We know that for PV=C

Now by putting the values
PV= 50 x 0.106

Where P is in KPa and V is in 
b)
PV= C
Take ln both sides
So 
lnP + lnV =lnC ( C is constant)
By differentiating

So

When P= 50 KPa

It indicates the slope of PV=C curve.
It unit is
.
Or we can say that
.
3 Newtons toward the right because Newton’s second law:
F = ma
15N - 12N = ma
3N = ma
(With the right being the positive direction and the left the negative direction)