Answer:
Demand curve for Sheila's plates and cups
[tex] Q = 22.5 - \frac{1}{2}P[/tex]
Explanation:
we have to write the demand function for Shiela's
[tex] Q = b - aP[/tex]
we solve for a solving for the line that cross two points:
[tex]\frac{P_2-P_1}{Q_2-Q_1} = a[/tex]
[tex]\frac{25 - 35}{35 - 30} = a[/tex]
[tex]\frac{-10}{5} = a[/tex]
[tex]- \frac{1}{2} = a[/tex]
Then we solve for b:
[tex] 35 = b - 1/2(25)[/tex]
[tex] 35 - 1/2(25) = b [/tex]
b = 22.5
Last we build the demand curve
[tex] Q = 22.5 - \frac{1}{2}P[/tex]