A rectangular prestressed beam 150 mm wide and 300mm deep is used over a effective span of 10m and the cable with zero eccentricity at the supports, linearly varying to 50mm at the centre carries an effective prestressing force of 500kn(Z=225 104). Evaluate stress due to prestressing?

A rectangular prestressed beam 150 mm wide and 300mm deep is used over

1.	A rectangular prestressed beam 150 mm wide and 300mm deep is used over a effective span of 10m and the cable with zero eccentricity at the supports, linearly varying to 50mm at the centre carries an effective prestressing force of 500kn(Z=225 104). Evaluate stress due to prestressing?
A.	22.2n/mm<sup>2</sup>
B.	42.2n/mm<sup>2</sup>
C.	32.2n/mm<sup>2</sup>
D.	52.2n/mm<sup>2</sup>
Answer» B. 42.2n/mm<sup>2</sup>