AP Physics: Electric Potential-Please Help-10 points for best answer?

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A negative charge -Q is uniformly distributed throughout the spherical volume of radius R. A positive point charge +Q is at the center of the sphere. Determine each of the following in terms of the quantities given and fundamental constants.

a. The electric field E outside the sphere at a distance r > R from the center.
b. The electric potential V outside the sphere at a distance r > R from the center.
c. The electric field inside the sphere at a distance r < R from the center.
d. The electric potential inside the sphere at a distance r < R from the center.

Note: I have done this problem but i am unsure of my answers. Thanks for any help you can provide.