Final answer:
The slope of a graph representing the nightly rate of a vacation rental indicates the additional cost per night, showing how much the price increases for each additional night stayed.
Step-by-step explanation:
If Angelina were to graph a line to show the nightly rate, the slope of the line would represent the additional cost per night. When graphing costs on a line, the y-intercept typically indicates a fixed, one-time fee (as shown in the examples provided where a cleaning company charges a one-time fee and a tutoring session has a one-time fee), while the slope illustrates the variable cost that increases with each unit of service (like the hourly rate for cleaning or tutoring, or the stock value decreasing over time).
So, in the context of a vacation rental, the slope would indicate how much the cost increases for each additional night stayed.
The y-intercept, on the other hand, might represent an initial fee, such as a cleaning fee or booking charge, that is paid regardless of the number of nights.
Therefore, the correct answer is that the slope represents the additional cost per night.