A$-6\mathrm{.}1$: A composite beam is made up of a $200mm300mm$ core $(E_c=14$GPa$)$

and an exterior cover sheet $(300(mm)12(mm),E_e=100$GPa$)$ on each side.

Allowable stresses in core and exterior sheets are $9\mathrm{.}5$MPa and $140$MPa, respec$-$

tively. The ratio of the maximum permissible bending moment about the $z-$axis to

that about the $y-$axis is most nearly:

$($A$)0\mathrm{.}5$

$($B$)0\mathrm{.}7$

$($C$)1\mathrm{.}2$

$($D$)1\mathrm{.}5$