Geometry Problem

The circle of center $P$ has radius 4.5cm and is tangent to $BC$ at point $S$ .

The circle of center $Q$ has radius 2cm and is tangent to $BC$ at point $U$ and it is also tangent to the circle that has center $P$ .

The circle of center $R$ is tangent to $BC$ at point $T$ and it is tangent to the other two circles.

What is the radius of the circle that has center $R$ ?

Give your answer to 2 decimal places.