Answer:
(c) I paid 200% of what I could have online and on sale.
Explanation:
The multiplier for a increase of a% is 1 + a/100.
In this question:
You paid twice, which means that the multiplier is 2. So
a is the increase, as a percent.



You had an increase of 100% on the price. Since the original amount was 100% you paid 100 + 100 = 200%(100% more, 2 times) of what you could have paid.
So the correct answer is:
(c) I paid 200% of what I could have online and on sale.