Answer:
200 nm
Explanation:
We need a constructive interference to see the bright reflection
we know that
where m=1 and
is the wavelength of the gasoline
so 
putting the value of m and
in thickness equation

so the thickness of the film will be 200 nm
Answer:
You can open a HTML document in internet explorer usually browsers can open HTML files.
Answer:
Try to restart your computer, if it doesn't work try looking up what to if anti-virus protection comes up randomly, without needing it.
Explanation:
Not Sure if you'll still get it even after restarting, but if it doesn't then hard shutdown the computer, So it could refresh it.