Please help and show working please

We have to build a schema of all the forces applied to the car:

We have air resistance and friction, both against the direction of motion.

We have gravity (due to the downhill angle) and motor force, acting in the direction of motion.

So, we can set up the equation

where F is the sum of all forces:

Where is the motor force, is the gravity force, is the friction force, and is the air resistance force (note that the signs depend on whether the force is along or against the direction of motion.

We can solve for as follows:

We know everything, except for . The formula for the force parallel to the direction of motion in a sloped plane with angle is

So, we can substitute:

the answer is a. at the equator