PROBLEM $1.$ Given with the beam dimensions:

$n=9$

$h=550mm$

$d=480mm$

$b=400mm$

Reinforced with $3-25mm$ dia. Rebars

a$.$ Assuming the concrete is uncracked, compute the bending stresses in the extreme fibers of the beam at $M=260kN-m.$

b$.$ Determine the cracking moments for the sections shown if $f^{\text{'}}c=28$MPa.

c$.$ Compute the flexural stresses in the concrete and steel for the beams shown using the transformed$-$area method at $M=$

$280kN-m.$

d$.$ Determine the allowable resisting moment of the beam, if the allowable stresses are $fc=25$MPa and $fs=120$MPa.