Robin fills a bathtub and then drains it. Use the following information to draw a detailed graph of the water level in the bathtub over time.
The water level starts at 0 cm.
After Robin turns on the taps, the water level rises at a rate of 0.5 cm/s for 10 s.
Robin turns off the tap at the 20 s mark.
The water level is constant for another 10 s. Then Robin pulls the plug, and the water level drops at a rate of 0.25 cm/s until the tub is empty.