Suppose a monopolist producing self-cleaning jackets can sell 20 jackets at $100, and 21 jackets at $98. the monopolist is unable to price discriminate, so in order to sell a total of 21 jackets, the price per jacket must be $98.

1-when charging $100 per jacket, total revenue is? :

2-when charging $98 per jacket, total revenue is? :

3-so the marginal revenue of selling the 21st jacket is? :

4-in the case of any firm facing a downward sloping demand curve, marginal revenue is always? :