Welcome to PF,
HOW does the centripetal acceleration depend on the speed and radius? If this is homework, it should be posted in the homeowork help section, whose posts have a template that forces you to include helpful things like *relevant equations* and your attempt at a solution (things that are helpful to YOU for arriving at a solution).
So, try varying each parameter and seeing what happens. If you double the speed, what happens to the centripetal acceleration (keeping the radius constant)? How about if you double the radius (keeping the speed constant)? On which variable does the acceleration seem to have a stronger dependence, the speed, or the inverse of the radius? (Hint: it's pretty obvious because one of them is a non-linear dependence)