Virial theorem for the age of a star of constant luminosity

1)

Using the virial theorem, derive an expression for the time required for
a star of uniform density and constant luminosity to reach its current
radius?

OTA please note my thinking so far for this problem is.

I think I need to start this problem using the viral theorem in the
form,



and luminosity is,



= Stefan-Boltzmann constant

Other equations to consider are,

(Kinetic energy)

(Gravitational potential energy)

I am obviously looking for an equation that incorporates all of the
above into one which expresses the time T taken for a star to reach
thermal equilibrium at radius R2 from radius R1. The difficulty is that
I do not know how to incorporate them into one simple equation.