Jonas has been living in the United Kingdom for the past four years while pursuing an undergraduate degree in Economics.
In each of the last four years, he has made trips back home to Germany for Christmas, Easter, and during his summer term break. In 2018, the price of a round-trip train ticket from London to Frankfurt decreased from €109 to €50.50. As a result, Jonas decided to purchase tickets to watch Les Misérables at the Queen’s Theatre in London.

a. Explain how Jonas’s demand for theater tickets can be affected by a fall in the price of rail tickets.

b. By using this example, explain why both income and substitution effects might be expected to increase the number of trips Jonas makes to Frankfurt.