A charter flight charges a fare of $$300$ per person plus $$6$ per person for each unsold seat on the plane. If the maximum capacity of the plane is $100$ passengers and if $x$ represents the number of unsold seats,

a$)$ develop an expression for the number of people flying on the flight,

b$)$ develop an expression for the total revenue received for the flight,

c$)$ the number of unsold seats that will produce the maximum revenue, and

d$)$ the maximum revenue.