Query in Independent population, unknown variances example of apples.

Hi team,
I had doubt in the section 5 of statistics course.
After testing the hypotheses whether NY apples are costlier than LA or not a question is given for checking whether the NY apples are 20% costlier than LA.

I get that we will be using (ny.mean - la.mean / la.mean) as the difference mean, if I am not wrong, but I needed the help with other statistic.

It would be great, if you could help me with that.
Thank you.
Kind Regards
Yuvraj.