A graph shows the limit to be 1/2.
https://www.desmos.com/calculator/qrf6ay47tw
Since the value of the function is the indeterminate form 0/0, L'Hôpital's rule applies. The ratio of derivatives of numerator and denominator is
.. x/
Evaluated at x=1, this is
.. 1/
= 1/2
To solve this, you divide the price by the amount of ounces, and find the one which results in the smallest number. That was B, $4.29 for 12 ounces.