Answer
a) $0.05x^2+20x-50$
b) The profit on $10$ calculators is $\$155$ and on 20 calculators it is $\$370$.
Work Step by Step
a) The profit can be obtained by subtracting the cost from the revenue:
$P=R-C=50x-0.05x^2-(50+30x-0.1x^2)=0.05x^2+20x-50$
b) Plugging in $x=10$, we get:
$C=0.05(10)^2+20(10)-50=155$
Plugging in $x=20$, we get:
$C=0.05(20)^2+20(20)-50=370$
