The answer to the part C:
Part C asking for APY ( Annual percentage yield )
APY is giving by the formula:

Where: r is the annual percentage rate.
k is the number of times each year that the interest is compounded.
Given: r = 3.6% = 0.036 , k = 4
Substitute with (r) and (k) into the formula of APY
So,

Rounding to 3 decimal places.
So, the answer will be APY = 3.649%