A timber is being designed with supports and loads as shown.

Given: $w=520\frac{N}{m}$

Knowing that the available stock consists of beams with an allowable normal stress of $12$ MPa and a rectangular cross section of $30$ mm width and depth $h$ varying from $80$ mm to $160$ mm in $10-mm$ increments, determine the most economical cross section that can be used. In part one, the maximum bending moment $=0\mathrm{.}945$ kN meters, and The location of Max bending Moment From a x$=2\mathrm{.}094$ m$.$

The most economical cross section that can be used is$?$