At time [math], in hours, a lake is covered with ice of thickness [math] cm, where [math].

1. How fast is the ice forming when [math]? When [math]? Give units.
when [math]:
when [math]:

2. If ice forms for [math], at what time in this interval is the ice thickest? At what time is the ice forming fastest? (Give units here, too.)
Ice is thickest at [math]
Ice is forming fastest at [math]