bear in mind that it goes with the "degree" of the polynomial.
It is unchanged because the same number would still be in the middle and there would still be the same amount of numbers
if
11,15,21,22,23,27,30 before 22 is the median
if
11,15,21,22,23,27,30 after 22 is still the median
The median is unchanged
The last question is is $1,250 because 30 percent of 50,000 is 15,000 and 15,000 divided by 12 months is 1,250