Please evaluate the correct answer of the given question

Question- Imagine that the magnetic field vectors in a certain region of space is always tangent to a circle drawn around the x axis perpendicular to that axis. The field has a magnitude of B=ar2, where r is the distance from the x axis and a is some constant. Consider a circular Amperian loop of radius R centered on and perpendicular to the x axis.

Part 1- Evaluate the circulation for this loop in terms of a and R, and explain why there are two possible values for the result.

I need experts assist to compute the circulation for given loop.