By Green's theorem,

where
is the circle
and
is the interior of
, or the disk
.
Convert to polar coordinates, taking

Then the work done by
on the particle is

Step-by-step explanation:
We can use the formula to find the number of moles. As ,
n = No. of particles/ N_A
n = 3.01× 10¹⁸/6.022 × 10²³
n = 1/2 / 10⁵
<h3>Hence the number of particles is 1/2 / 10⁵ </h3>
D would be the correct answer.
Explanation
a^2+b^2=c^2
4^2+3^2=c^2
16+9
25 units