A box beam is shown below. The beam is made with normal weight concrete

$($NWC$).$ The concrete compressive strength and the rebars yield strength are

$f^{\text{'}}c=4$ksi and $fy=60$ ksi, respectively.

The maximum tension stress in the concrete due to a service bending

moment $M=2$ kip$-$ft is

$3\mathrm{.}60$ psf

$8\mathrm{.}64$ psi

$11\mathrm{.}1$ psi

$25\mathrm{.}0$ psi