Let's assume they meant C=40 degrees. With an angle like that they're asking for approximation; we'll oblige.
The circumradius is the product of the triangle sides divided by four times the area.
Here we have remaining side given by the Law of Cosines.
The area is
The circumradius is
The circumradius is the product of the triangle sides divided by four times the area.
Here we have remaining side given by the Law of Cosines.
The area is
The circumradius is