Explanation:
Below is an attachment containing the solution.
Before getting an answer for it first we have to understand nuclear fusion.
Nuclear fusion is a thermo-nuclear reaction in which two light unstable nuclei will form a heavy stable nuclei. In this process there will be some mass defect which will be converted into energy as per Einstein's mass energy equivalence theorem.
The theorem is stated as
where c is the velocity of light and m is the mass converted into energy.
One take an example of fusion in sun where 4 hydrogen atoms combine to form a helium nucleus which are explained below-



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Here
is the positron.
In this process very high temperature is needed which is approximately equal to the temperature of the sun i.e 
Such temperature is very difficult to initiate the reaction on the earth surface. It should be carried out in an sustainable way also .Otherwise It will cause nuclear hazards.
Ok so the expression that you will be doing is water-water+object. The actual expression is 120-80. The answer would be 40mL. Remember, don't forget your units! :)
<span>Even though the Sun has a greater mass than Earth, the Moon orbits Earth because it's closer to the Earth than to the Sun. Because of this proximity between the Earth and the Moon, the Earth has a stronger gravitational pull than the Sun does. Furthermore, the Earth's mass is 81 times that of the Moon, and so at this proximity, it is more than able to overpower what pull the Sun exerts on the Moon.</span>