Quantizing Radii of a Mass in Circular Orbit

[quickclick330]

This is yet another sample exam problem which I don't quite know how to approach. Any help would be greatly appreciated.

5) Consider an object of mass m that moves in a circular orbit caused by a central
force given by F=-kr, where k is a constant. Suppose that the Bohr quantization
condition (L=mvr=nh) is applied to this motion. What are the allowed radii?
a. rn=(n4h4/m2k)1/4, n = 1,2,…
b. rn=(n2h2/mk)1/4, n = 1,2,…
c. rn=(n2h2/mk)1/3, n = 1,2,…
d. rn=(n2h2/mk)1/2, n = 1,2,…
e. Not enough information given to compute levels
f. Radii for this force law cannot be quantized

 

[Avodyne]

You first find v by requiring the force to produce the centrepital acceleration of circular motion. Then set L=mvr=nh and solve for r.