Answer:
The magnification is 
Explanation:
From the question we are told that
The power of the lens is 
Generally 
The object distance is 
the negative sign is because the distance is measured in the opposite direction of incident light (i.e away )
Generally the focal length is mathematically represented as
=>
=> 
converting to cm
=> 
Generally from lens equation we have that
=> 
=> 
Generally the magnification is mathematically represented as
=> 
=>
its c!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
B. By vibrations in wires or strings
Empirical formula of compound is XF3
Compound consist of 65% F
In 100g of compound there is 65 g of F
= 65 / 19 moles of Fluorine = 3.421 moles
So moles of X = 3.421 / 3 = 1.140 moles
And in 100 g X
consist of 35 g
So the molar mass of X = 35 / 1.140 = 30.71 g = 31
approximately
And it is the mass of phosphorus
So the empirical formula for the compound is PX3
