Georgia and Lauren are economics students who go to a karate class together.

Both have to choose how many classes to go to per week. Each class costs $20. The accompanying table shows Georgia’s and Lauren’s estimates of the marginal benefit that each of them gets from each class per week.

a. Use marginal analysis to find Lauren’s optimal number of karate classes per week. Explain your answer.

b. Use marginal analysis to find Georgia’s optimal number of karate classes per week. Explain your answer.