A rectangular tank contained some water at first. A tap was then turned on to fill the tank completely with water. The tap was turned off at the end of 48 minutes. The graph below shows the amount of water in the tank at the end of 48 minutes.

1. Identify the initial and final volume of water during the filling phase from the graph

From the graph, at $t = 0$ min, the volume is $20$ L.
The tank is completely filled at $t = 24$ min, where the volume is $110$ L.

2. Calculate the total volume of water that flowed from the tap

Total volume flowed = $110 - 20 = 90$ L

3. Calculate the rate of water flow per minute

Rate = $\frac{90}{24} = 3.75$ L/min

1. Determine the duration for which the water overflowed

The tank is completely filled at $24$ minutes. The tap was turned off at $48$ minutes.
Time during which water overflowed = $48 - 24 = 24$ minutes.

2. Calculate the volume of water that overflowed

From the graph, the amount of water that flowed from the tap in the first $24$ minutes is $110 - 20 = 90$ L.
Since the tap flows at a constant rate, the amount of water that flowed (and overflowed) in the next $24$ minutes is also $90$ L.
Alternatively, using the rate from part (a) ($3.75$ L/min):
Volume overflowed = $3.75 \times 24 = 90$ L.