The $612-$in$.$ timber beam has been strengthened by bolting to it the steel reinforcement shown. The modulus of elasticity for wood is

$1\mathrm{.}8{10}^6$ and for steel is $29{10}^6$ psi. Knowing that the beam is bent about a horizontal axis by a couple of moment $M=458$

kip.in$.,$

determine the radius of curvature caused by the couple.

The radius of curvature caused by the couple is $\_\_\_\_$ ft$?$