A cinema hall has a capacity of 150 seats. The owner can offer students a discount on the price when they show their student IDs. The demand for tickets from students is Ds = 220 - 40Ps;
where Ps is the price of tickets for students after the discount.
The demand for tickets for non-students is Dn = 140 - 20Pn;
where Pn is the price of tickets for non-students.
i. What is the maximum prot the owner can make?
ii. What is the maximum prot he could make if the demand functions of students and non-students were interchanged?