Question 1068413
(x,y) for x number of deserts and y price of a desert


Points  (80,7) and (40,9).
y=mx+b
b=y-mx
{{{y=((9-7)/(40-80))x+(9+(1/20)40)}}}
{{{y=-(1/20)x+9+2}}}
{{{y=-(1/20)x+11}}}


Calling this price function f,
{{{highlight(f(x)=-(1/20)x+11)}}}



SELL x DESERTS
Cost {{{2x}}}
Revenue  {{{x*f(x)=x(-(1/20)x+11)=-x^2/20+11x}}}
-
PROFIT FUNCTION  {{{P(x)=-x^2/20+11x-2x}}}
or simplified,
{{{highlight(P(x)=-x^2/20+9x)}}}


You can look for the maximum P.