Im positive that the answer is b
Answer:
The equilibrium position for the third charge is 69.28 cm
Explanation:
Given;
q₁ = -5.00 x 10⁻⁹ C
q₂ = -2.00 x 10⁻⁹ C
q₃ = 15.00 x 10⁻⁹ C
distance between q₁ and q₂ = 40.0 cm = 0.4 m
(-q₁)--------------------------------------(-q₂)---------------------------------(+q₃)
At equilibrium the repulsive force between q₁ and q₂ must be equal to attractive force between q₂ and q₃
According to Coulomb's law, repulsive or attractive force between charges is calculated as;

where;
F is repulsive or attractive force between charges
K is Coulomb's constant = 8.99 x 10⁹ Nm²/c²
r₁ is the distance between q₁ and q₂
q₁, q₂ and q₃ are the charge
distance between q₂ and q₃, r₂ is calculated as;

Therefore, the equilibrium position for the third charge is 69.28 cm
Machine C. Machine A has an efficiency of 250/1000 = 0.25 = 25%, Machine B's efficiency is 350/500 = 0.7 = 70% and Machine C has an efficiency of 150/200 = 0.75 = 75%.
The reason as to why the substage condenser does not need to be included in computing the magnification and the only component needed is the ocular lens and the objective lenses is because the condenser is only responsible for gathering light and it does not contribute with the magnification of the object under the microscope.
The qualifications boil down to: College education.
In most university or industrial research organizations, you might be able to work there as a member of the team who doesn't get much pay or much respect, with research going on all around you directed by other people, after you've gotten you Master's degree.
But you really don't have a shot at leading anything, or having much to say about what's being researched or how, until you have a PhD degree in the field where you'd like to do the research.
(Did I mention how proud I was to be present about 6 weeks ago, in a land far away, when my daughter was awarded a PhD degree in Molecular Biology ? I didn't want to let you get away without hearing about that.)