Question

A fixed end tube is 50 mm long. In the middle of the beam a 20 N torque is applied. If the polar moment of area of the tube = a mm^4 and the Shear Modulus of the material = p N/mm^2
Calculate the angle through which the tube rotates.

I understand that I need to use T/J = Gθ/L but I am unsure what to do about the torque being applied in the middle?
Thank you