This PR collects feedback from the reading group on intro_supply_demand.

Code

• Remove classes and use NamedTuple
• Add more explanation and comments on functions we used in the exercise scipy.optimize.minimize_scalar and scipy.optimize.newton

Content

• Explain willingness to pay and the actual price. We can add a visualization showing consumers' willingness to pay and calculate the discrepancy to the actual price (Can we run a simulation?).