Do you not understand how to solve for the answer?
The answer is 6.
Add 4 then divide 2. You should have 18 after you do that, subtract 10 then multiply 20. You then have 6.
I. the type of wave ... electromagnetic or mechanical
(II. amplitude doesn't influence the speed of any wave)
III. the medium in which the wave travels ... completely determines the wave speed
Answer:

Explanation:
From the question we are told that
The number of turns is 
The radius is 
The position from the center consider is x = 3.45 cm = 0.0345 m
The induced emf is 
Generally according to Gauss law

=> 
Where A is the cross-sectional area of the solenoid which is mathematically represented as

=> 
=>
ggl;
Here
is the permeability of free space with value

=> 
=> 