Assume that in one month, you get 64 mm of rainfall, where a 30 m^2 tank collects the water. Let's say a garden bed has a top surface area of 14 m^2 and a maximum volume of 5 m^3. The plants need 24 liters per square meter to grow, and they are watered every 7 days. At the end of the month, how much water is left over in the tank, if any?