Generate the piece-wise function for the following problem:
A businessperson maintains inventory over a particular 30-day month as follows:
Days Units
days 1-9 30 units
days 10-15 17 units
days 16-23 12 units
days 24-30 Steadily decreasing from 12 units to 0 units.
Sketch the graph of the inventory as a function of time t (days). At what times is the graph discontinuous?