You have just opened a new nightclub Russ Techno Pitstop but
     You have just opened a new nightclub, Russ\' Techno Pitstop, but are unsure of how high to set the cover charge (entrance fee). One week you charged $7 per guest and averaged 180 guests per night. The next week you charged $12 per guest and averaged 130 guests per night.  (a) Find a linear demand equation showing the number of guests q per night as a function of the cover charge p.  q(p) =  (b) Find the nightly revenue R as a function of the cover charge p.  R(p) =  (c) The club will provide two free non-alcoholic drinks for each guest, costing the club $3 per head. In addition, the nightly overheads (rent, salaries, dancers, DJ, etc.) amount to $1, 000. Find the cost C as a function of the cover charge p.  C(p) =  (d) Now find the profit in terms of the cover charge p.  P(p) =  Determine the entrance fee you should charge for a maximum profit.  p = $  per guest
 
  
  Solution
(a)
2 points of linear demand function are (p1,q1)=(7,180),(p2,q2) =(12,130)
equation of function:
q-180=[(130-180)/(12-7)](p-7)
=>q-180=[-50/5](p-7)
=>q-180=-10(p-7)
=>q-180=-10p+70
=>q=-10p+250
so demand equation is q(p) =-10p+250
(b)
revenue ,R=pq
revenue ,R=p(-10p+250)
revenue ,R=(-10p2+250p)
revenue function is R(p)=(-10p2+250p)
(c)
cost,C=1000+ 3q
cost,C=1000+ 3(-10p+250)
cost,C=1000-30p+750
cost,C=1750-30p
cost function ,C(p)=1750-30p
(d)
profit,P(p)=R(p)-C(p)
P(p)=(-10p2+250p)-(1750-30p)
P(p)=-10p2+250p-1750+30p
P(p)=-10p2+280p-1750
P(p)=-10(p2-28p) -1750
P(p)=-10(p2-28p+196-196) -1750
P(p)=-10(p2-28p+196) +1960 -1750
P(p)=-10(p-14)2 +210
vertex is (14,210)
$14 per guest should be charged for a maximum profit


