The demand for your college newspaper is 2200 copies each week if the paper is given away free of charge and drops to 1000 each week if the charge is 10/copy. However, the university is only prepared to supply 600 copies each week free of charge but will supply 1400 each week at 20/copy.

Write down the associated linear demand function.
Write down the associated linear supply function.

D = Demand (# of copies)

S = Supply (# of copies)
p = price in cents
======================
D = 2200 - 120 p
S = 600 + 40 p

Although they didn't ask for it,
D = S when 1600 = 160 p
p = 10 cents

To write down the associated linear demand function, we need to determine how the quantity demanded changes based on the price of the newspaper. In this case, we are given two sets of price and quantity demanded:

Free of charge: Q = 2200 copies
Price = 0

Charge of 10/copy: Q = 1000 copies
Price = 10

We can use these two points to find the slope of the demand function.

Using the formula for slope:
Slope (m) = (change in quantity)/(change in price)
= (Q2 - Q1)/(P2 - P1)
= (1000 - 2200)/(10 - 0)
= -1200/10
= -120

Now that we have the slope, we can choose one of the points to substitute into the slope-intercept form of a linear equation (y = mx + b) to find the value of the y-intercept (b).

Using the point (Q=2200, P=0):
2200 = -120(0) + b
2200 = b

Now we can write down the demand function:
Demand Function: Q = -120P + 2200

To write down the associated linear supply function, we can follow a similar process. We have two sets of price and quantity supplied:

Supply of 600 copies free of charge:
Q = 600 copies
Price = 0

Supply of 1400 copies at 20/copy:
Q = 1400 copies
Price = 20

Again, we can use these two points to find the slope of the supply function:

Slope (m) = (change in quantity)/(change in price)
= (Q2 - Q1)/(P2 - P1)
= (1400 - 600)/(20 - 0)
= 800/20
= 40

Using the point (Q=600, P=0):
600 = 40(0) + b
600 = b

Now we can write down the supply function:
Supply Function: Q = 40P + 600