2. San Francisco Bay can be conceptually divided into two parts: the North Bay, which includes all of the water north of the Bay Bridge, and the South Bay (take a look at google maps to see this; the Bay Bridge is highway 80). The Sacramento River is the main source of fresh water flowing into the North Bay, at an average rate of 7107m3/ day. There are no significant natural river flows in to (or out of) the South Bay but assume that sewage treatment plants discharge into the South Bay 107m3/ day of water. The gross rate of seawater flow in to the [North] Bay from the ocean through the Golden Gate averages 3.000109m3/ day. Water can exit the North Bay either by outflow through the Golden Gate, or by evaporation, or by flow to the South Bay. Consider the year 2050, when global warming has set in with a vengeance. The South and North Bays each lose water via evaporation at an average rate of 4106m3/ day (considerably higher than the current rate). Nevertheless, the daily-averaged stock of water in the Bay is unchanged from year to year because it is connected to the oceans. a. Draw a box model of the Bays, labeling all inflows, outflows. (10 pts.) b. Calculate the average net flow, in m3/ day through the Golden Gate. (10 pts.)