Problem $19-16($Static$)$

A garden store prepares various grades of pine bark for mulch: nuggets $(x_1),$ mini$-$nuggets $(x_2),$ and chips $(x_3).$ The process requires pine bark, machine time, labor time, and storage space. The following model has been developed.

Maximize $,9x_1+9x_2+6x_3(profit)$

Subject to

a$-1.$ What is the marginal value of a pound of pine bark? $($Round your answer to $2$ decimal places.$)$

The marginal value of a pound of bark is

a$-2.$ Over what range is this price value appropriate?

This marginal value is in effect from

lbs$.$ to

lbs$.$ of bark.