A concrete beam prestressed with a parabolic tendon is shown in the sketch. The eccentricity of the tendon is measured from the centroid of the cross-section. The applied prestressing force at service is $1620$ kN. The uniformly distributed load of $45$ kN/m includes the self-weight

The stress (in $N/mm^2$) in the bottom fibre at mid-span is

1. tensile $2.90$
2. compressive $2.90$
3. tensile $4.32$
4. compressive $4.32$