A rectangular beam of $300$mm width and $600$mm depth is used over an effective span of $12$m tosupportuniformly distributed load of $12$kN$/$m$,$ which includes the self$-$weight of the beam. The beam isprestressed by a cable having high tensile wires of $2000$ mm $2$ area stressed to $800$N$/$mm $2.$The cableis located at a distance of $175$mm from the soffit of the beam. Determine thelocation of the thurst lineat the centre and quarter span section of the beam.