Answer:
Hey
I am sure from what i know that your answer should be the following:
Modern technology is deeply tied to efficiancy and speed. Think of the knew 5G network it gives us very fast internet, or perhaps our very nessisitys such as our phone or cumputer. On a phone you have so much (thats to say you can acces alot easly); pictures videos dictionarys video games etc etc.
The electron is accelerated through a potential difference of

, so the kinetic energy gained by the electron is equal to its variation of electrical potential energy:

where
m is the electron mass
v is the final speed of the electron
e is the electron charge

is the potential difference
Re-arranging this equation, we can find the speed of the electron before entering the magnetic field:

Now the electron enters the magnetic field. The Lorentz force provides the centripetal force that keeps the electron in circular orbit:

where B is the intensity of the magnetic field and r is the orbital radius. Since the radius is r=25 cm=0.25 m, we can re-arrange this equation to find B:
Answer:
887.1Hz
Explanation:
Given parameters:
Speed of sound wave = 330m/s
Wavelength = 0.372m
Unknown:
Frequency = ?
Solution:
To solve this problem, we use the expression below:
Speed = Frequency x wavelength
330 = Frequency x 0.372
Frequency = 887.1Hz
The correct field line would be A.
Explanation:
Efficiency is defined as the ratio between the useful output over the total amount consumed. 
The fan does 500W of useful work while wasting 300 W. The total power consumption is 800 W (500 + 300).