Solve the Problem $1,668 \mathrm { lb }$ Find the Maximum Load That Can Be Safely Supported

Solve the problem.
-The strength of a wooden beam varies jointly as the width of the beam and the square of the thickness of the beam, and inversely as the length of the beam. A beam that is 48 in. long, 6 in. wide, and 4 in. thick can support a load of $1,668 \mathrm { lb }$ . Find the maximum load that can be safely supported by a board that is $8 \mathrm { in }$ . wide, $120 \mathrm { in }$ . long, and 5 in. thick.

A) $1,529 \mathrm { lb }$
B) $1,676 \mathrm { lb }$
C) $1,390 \mathrm { lb }$
D) $1,533 \mathrm { lb }$