We are to look for the input work that would yield 50 J when it is only at 65% efficiency. To show this mathematically: Input work x (65/100) = 50 J. So to find the input work, we are to divide 50 J by (65/100). This is shown below:
Input work = 50 / (65/100) = 76.92 J
Therefore, the input work needed is 76.92 J.
