please answer this question

I In the diagram1 eleven circles of four different sizes are drawn. Each circle labelled W has radius 1, each circle labelled X has radius 2, the circle labelled Y has radius 4, and the circle labelled Z has radius 1*. Each of the circles labelled W or X is tangent to three other circles. The circle labelled Y is tangent to all ten of the other circles. The circle labelled Z is tangent to three other circles. Determine positive integers s and t for which r = 3. )Suppose that c is a positive integer. Dene f(c) to be the number of pairs ((1,1)) of positive integers with c