Given the total revenue $=R(x)=3x^2+36x+5$.
If the Total Revenue is given by $f(x)$, the Marginal Revenue is the rate of change of total revenue and is nothing but the first order derivative of the function $\large \frac{df(x)}{dx}$
$\Rightarrow$ Differentiating $R(x)$, we get $\large \frac{dR(x)}{dx}$$ = 6x+36$
If $x=5$, Marginal revenue $= 6 (5) + 36$
Therefore, Marginal revenue $= 30+36 = 66$.
The concern over the welfare of the employees by the employer.