Make sure the triple beam balance is at 0 before you begin.
We can solve the problem by using Snell's law, which states

where

is the refractive index of the first medium

is the angle of incidence

is the refractive index of the second medium

is the angle of refraction
In our problem,

(refractive index of air),

and

(refractive index of carbon disulfide), therefore we can re-arrange the previous equation to calculate the angle of refraction:

From which we find
When you add up (20N down) and (10N up),
you get a sum of (10N down).
The mass of the object has no effect on the forces.
Now ... I see 5 points for the answer.
Where are the other 25 coming from ?
Answer:
The correct answer is - 43%.
Explanation: The increase in CO2 between these two suggested periods is approximately 43%. Even though it is a natural process that the CO2 levels vary in the atmosphere, still this is not the same case nowadays. Nowadays, or rather in the past few decades, apart from the natural increase of CO2 in the atmosphere, it has seen a much more increased levels because of the human activity. The industrial facilities and the vehicles, the cutting of the forests and burning the wood (there's both release of CO2 from the burning of the trees and loss of natural accumulator of the CO2), are just some of the more important human activities that contribute to a significant rise in the CO2 levels.
'Pressure' is (force) / (area).
The only choice with those units is #1 .