Find mass flow rate using heat differential

1. The problem statement, all variables and given/known data

An experimental power plant at the Natural Energy Laboratory of Hawaii generates electricity from the temperature gradient of the ocean. The surface and deep-water temperatures are 25°C and 7°C respectively.

The cold water that enters the plant leaves it at a temperature of 12°C What must be the flow rate of cold water through the system? Give your answer in kg/s & L/s.

dm/dt = ?

2. Relevant equations

W = QH - QC
e = 1 - TC / TH
cwater = 4190 J/kg*K

3. The attempt at a solution

I understand that it takes a certain amount of time to raise the water from 7°C to 12°C, but I don't know how to find that or how to relate it to a flow rate.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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 Tags carnot cycle, heat, mass flow rate