Question $(6)$:

Water flows between two adjacent parts of a vertically sided service reservoir through a submerged $0\mathrm{.}3m$ diameter orifice $)$ in a common dividing wall. The first reservoir measures $45m$ by $30m$ in plan and initially contains water to a height of $5m$ above the center of the orifice. The second tank is $20m$ by $30m$ in plan and the initial water level can be assumed to be at the same height as the center of the orifice. Assuming that there is no other flow into or out of the reservoirs, Find:

a$)$ How long it will take for the two water levels in the tanks to become equal?

b$)$ What is the final depth of water in the tanks, measured above the center of the orifice?