Please explain all the steps including the calculation for the revenue

Table: Tutoring Sigmund tutors five students for the introductory psychology class. The students differ in their willingness to pay for a one-hour session. The second column of the table shows their willingness to pay for a one-hour session. Sigmund has estimated his costs of providing tutoring hours (he has no sunk costs) and these costs appear in the last column. a) If Sigmund can charge all students their willingness to pay, what is Sigmund's optimal number of tutoring hours? b) If he can charge all students their willingness to pay, at the optimal hours of tutoring, what is Sigmund's total profit? c) If the college requires all tutors to register with the dean and charges each tutor $10 to register, what is Sigmund's optimal number of tutoring hours? d) If the college requires all tutors to register with the dean and charges each tutor $10 to register and if Sigmund can charge all students their willingness to pay, what will his total profit from tutoring be