What is the difference between a lump sum and per unit subsidy? Here, an economics instructor explains how these each affect cost curves, and more specifically marginal cost, by illustrating the concept on a whiteboard. 

Here is a fantastic resource in which you will watch as an instructor models a simulation conducted in an economics class on the four market structures (perfect competition, monopolistic competition, oligopoly, monopoly).

Reviews monopolies and explains graphical representations of monopolies.

Using some basic calculus to show that marginal revenue has twice the slope of the demand curve for a monopolist. [4:56]

Showing that what is optimal for the monopolist is not optimal for society.

Plotting the marginal revenue curve for a monopolist. [8:31]

Discusses how a monopolist would rationally optimize profits.

A discussion of what would happen if there were only one airline, creating a situation that would be the opposite of perfect competition.

In this video [10:21], we review the key features, behavior, and consequences of a monopoly.