A child fills a pail by using a water hose. After finishing, the child plays in a sandbox for a while before tipping the pail over to empty it. If [math] gives the volume of the water in the pail at time [math], then the figure below shows [math] as a function of [math].

At what time does the child:
A. Begin to fill the pail? [math]
B. Finish filling the pail? [math]
C. Tip the pail over? [math]

(What would the graph of [math] look like if the child filled the pail by using a play shovel to repeatedly scoop water from a larger bucket and dump it in the pail instead of using a hose?)