The quantity demanded x each month of Russo Espresso Makers
Solution
(a) The typical linear demand equation is as follows -
Q = a - bP
Where,
Q = quantity demanded
P = Price
b = Slope
a = Y-intercept
In the given case, two price and quantity points are given.
Quantity is taken on X-axis and price is taken on Y-axis.
So, points can be written as follows -
(250, $140) and (500, $130)
Calculating Slope -
b = (y2 - y1)/(x2 - x1) = (130 - 140)/(500 - 250) = -0.04
Using point - slope equation,
y - 140 = -0.04(q - 250)
y = -0.04q + 10 + 140
y = -0.04q + 150
Replacing y with p as y represent price in given case.
p = -0.04q + 150
The demand equation is -: p = -0.04q + 150
(b) The typical linear supply equation is as follows -
Q = a + bP
Where,
Q = quantity supplied
P = Price
b = Slope
a = Y-intercept
In the given case, two price and quantity points are given.
Quantity is taken on X-axis and price is taken on Y-axis.
So, points can be written as follows -
(750, $40) and (3,000, $70)
Calculating Slope -
b = (y2 - y1)/(x2 - x1) = (70 - 40)/(3,000 - 750) = 0.01
using the point-slope formula for a line -
y - 40 = 0.01(q - 70)
y - 40 = 0.01q - 0.7
y = 0.01q + 39.3
Replacing y with p as y represent price in given case.
p = 0.01q + 39.3
The supply equation is -: p = 0.01q + 39.3
(c) Equilibrium is attained when supply equals demand.
Equating demand and supply equations to ascertain equilibrium quantity -
-0.04q + 150 = 0.01q + 39.3
-0.05q = -110.7
q = 2,214
The equilibrium quantity is 2,214 units.
Calculating equilibirum price -
p = -0.04q + 150 = (-0.04*2,214) + 150 = -88.56 + 150 = 61.44
The equilibrium price is $61.44.

