Consider the following linear programming problem, which maximizes profit for two products: regular $($R$)$ and super $($S$)$:

MAX $5$R $+75S$

s$.$t$.$

$1\mathrm{.}2R+1\mathrm{.}6S600$ assembly $($hours$)$

$0\mathrm{.}8R+0\mathrm{.}5S300$ paint $($hours$)$

$0\mathrm{.}16R+0\mathrm{.}4S100$ inspection $($hours$)$

$R,S0$

the upper limit of the regular product $($R$)$ objective function coefficient $($profit of R$)$ is