A rectangular beam is fabricated by nailing together three pieces of dimension lumber as shown in the figure. Each board has a width

of $b=4\mathrm{.}25in.$ and a depth of $d=1\mathrm{.}50$ in$.$ Pairs of nails are driven along the beam at a spacing of $s,$ and each nail can safely transmit a

force of $125lb$ in direct shear. The beam is simply supported and carries a load of $1040lb$ at the center of a $7\mathrm{.}3ft$ span. Determine the

maximum spacing $s($along the length of the beam$)$ permitted for each pair of nails.

$s=$

in$.$