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 $V(t)$ gives the volume of the water in the pail at time $t$, then the figure below shows $V'(t)$ as a function of $t$.

At what time does the child:
A. Begin to fill the pail? $t =$
B. Finish filling the pail? $t =$
C. Tip the pail over? $t =$

(What would the graph of $V'(t)$ 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?)