From the characteristics of this decrease in water content, it can be seen that the decrease in water content for each treatment follows the following equation:

$Y=A{x}^3+B{x}^2+Cx+D$

$\backslash$table$[[$Parameter$,$CL$,$BL$,$SM$,$AA$],[$A$,-4\mathrm{.}3E-07,2\mathrm{.}71E-06,6\mathrm{.}94E-06,7\mathrm{.}44E-06$

Help the company determine:

The function of the rate of decrease in moisture content at $t=330$ minutes, and the critical points of decreasing water content during the drying process using $4$ kinds of pre$-$drying treatments.