C$2$: A pretensioned beam with a rectangular cross section is to be designed to support two superimposed concentrated loads of $175kN$ for each located at the third points of a $9m$ simple span. If the ACI code stress limits should be applied, find the required section dimensions, prestressing force and eccentricity. Find also the required number of $12\mathrm{.}7mm$ dia, $7-$wire strands with fpu$=1724$MPa and an area of $92\mathrm{.}9m{m}^2$ per strand. Use $f^{\text{'}}c=35$ MPa,$f^{\text{'}}ci=25$MPa. The concrete unit weight is $(24k\frac{N}{m^3})$ and effective prestress ratio $R=0\mathrm{.}8.$ Compute the cracking moment capacity of the beam.

$(50$ Marks$)$

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