Sit. A plain concrete beam having a trapezoidal section with a hollow circular portion of diameter $150mm,$ the center of which is located at mid$-$height, has a width of $300mm$ at the top and $200mm$ at the bottom. The overall depth of the beam is $600mm.$ The tensile strength of concrete is $ft=3$MPa and ultimate strength $f^{\text{'}}c=20$MPa.

$27.$ Determine the positive bending moment in $kN.m$ that causes the section to crack.

a$.38\mathrm{.}74$

b$.4697$

c$.49\mathrm{.}64$

d$.43\mathrm{.}11$

$28.$ What is the maximum bending stress in compression in MPa upon cracking?

a$.2\mathrm{.}46$

b$.2\mathrm{.}58$

c$.2\mathrm{.}74$

d$.3\mathrm{.}15$

$29.$ If the section is reinforced with $3-25mm$ at bottom. Determine the cracking moment using NSCP Provosion.

a$.38\mathrm{.}74$

b$.40\mathrm{.}97$

c$.49\mathrm{.}64-$

d$.43\mathrm{.}11$