To calculate the efficiency of the electrochemical cell, we need to determine the power output and the power input, and then divide the output by the input.First, let's find the power output P_out . The power output can be calculated using the formula:P_out = E_cell * Iwhere E_cell is the cell potential and I is the current.In this case, E_cell = 0.60V and I = 2.5A. Therefore,P_out = 0.60V * 2.5A = 1.5WNext, let's find the power input P_in . The power input can be calculated using the formula:P_in = E_standard - E_loss * Iwhere E_standard is the standard potential and E_loss is the potential loss due to internal resistance.We can calculate E_loss using Ohm's law:E_loss = I * Rwhere R is the internal resistance.In this case, I = 2.5A and R = 1.2. Therefore,E_loss = 2.5A * 1.2 = 3.0VNow, we can calculate P_in:P_in = 0.80V - 3.0V * 2.5A = -5.5WHowever, the power input should be positive. Since the cell potential drops to 0.60V, the actual power input should be:P_in = 0.80V * 2.5A = 2.0WFinally, we can calculate the efficiency of the electrochemical cell:Efficiency = P_out / P_in * 100%Efficiency = 1.5W / 2.0W * 100% = 75%The efficiency of the electrochemical cell is 75%.