Question

Help, what even is this?

Answer 1

This is known as a piecewise function. It's a function that depends on what t is valued at. There are three cases

If $0 \ \textless \ t \le 30$ then f(t) = 0. This means that for the first 30 minutes, the cost is $0, in other words the first half hour is free.

If $30 \ \textless \ t \le 90$ then f(t) = 5 indicating that the cost is $5 for the entire span from 30 minutes to 90 minutes (excluding t = 30 but including t = 90). Choice B is not the answer because the cost isn't $5 per minute. The cost for this entire timespan is simply $5

Finally, if t > 90, then f(t) = 10 telling us that any time value over 90 minutes will have the cost be $10. This is why the answer is choice D