Answer:
Part a)

Part b)

So density of atmosphere at Martian Surface is very less than the density at Earth.
Explanation:
Part a)
As per ideal gas equation we know that

here we know that Martian atmosphere is equivalent to that of carbon
so we will have


now we will have


Part b)
Now for the earth surface the density of air is given for


so we will have



So density of atmosphere at Martian Surface is very less than the density at Earth.
B 0.4 m should be correct if not it is A
C
Because it’s B-A if u reared the question u will understand
The initial kinetic energy of the boat and its rider is

After Sam stops it, the final kinetic energy of the boat+rider is

because its final velocity is zero.
For the law of conservation of energy, the work done by Sam is the variation of kinetic energy of the system:

where the negative sign is due to the fact that the force Sam is applying goes against the direction of motion of the boat.