A DC electric heater is placed inside an insulated tube where water is flowing steadily . Two temperature sensors are placed before and after the heater. Their readings are 25°C and 90°C. A Voltmeter and an Ammeter are connected to the heater. Their readings are 220 V and 5 A, respectively. What is the water mass flow rate inside this tube and its absolute uncertainty? Assume that all the electrical power is converted to heat inside the heater, and all the heat is then transferred to the water without any losses. The accuracies of the used devices are as follows: Temperature ±1°C, Voltage ±2%, and current ±1%.
This flowing water is used to fill 
ُ five identical  tanks. A stopwatch is used to measure the filling period ُ for each tank. The filling periods are as follows: 5, 5.05, 5.3, 5.1, and 5.2 min. The stopwatch has an accuracy of ±0.1 s. What is the volume of each tank (In liters) and its total uncertainty?