A local tutor has provided the following description of their tutoring services:

"I offer private GCSE Physics tutoring to local students. I charge based on the duration of the lesson, not how many topics are covered. If a student brings a classmate to study with them, I don't charge any extra. I prefer to teach in the evenings because I work at a local high school during the day. I need a software system to help me keep track of how much money I am owed by each student. Luckily, all of my students have unique student ID numbers, so it is very easy to identify them in the system. I charge £25 for every 45 minutes of tutoring, and I always round this up to the next 45-minute block (for example, a 50-minute lesson would be two 45-minute charges, or £50)."

The developer has decided that the following two points are the only important details from the client's request:

• The charge is based on duration and not how many topics are covered.
• The charge is £25 every 45 minutes.