Step-by-step explanation:
It is given that, your boss tells you that she needs a decision by the end of the day about the machine you want to purchase for your new operation.
Option 1.
This $5,000 machine is supplied energy at a rate of 1,900 W and does useful work at a rate of 1,786 W.

is power output and power input respectively
Here, output power is 1786 W and input power is 1900 W

Option 2.
This $4,500 machine is supplied energy at a rate of 1,450 W and does useful work at a rate of 1,300 W.
Here, output power is 1300 W and input power is 1450 W
So,

Option 3.
This $4,750 machine is supplied energy at a rate of 1950 W and does useful work at a rate of 1833 W.
Here, output power is 1833 W and input power is 1950 W

Option 4.
This $4,750 machine is supplied energy at a rate of 2,000 W and does useful work at a rate of 1,822 W.
Here, output power is 1822 W and input power is 2000 W

The efficiency of machine in option (1) and (3) is same i.e. 94% but the cost of c is less and is providing maximum efficiency. Hence, the correct option is (3).