A student uses a wheelchair to get around campus, which she travels to on a public bus. She boards the bus using a motorized lift attached near the bus door. The electric lift motor uses 1.4 kilojoules of energy to raise the student and wheelchair from the sidewalk to the level of the bus interior, a total displacement of 0.75 meters. If the mass of the
wheelchair is 20 kilograms and the mass of the student and her belonqings is 60 kilograms, what is the efficiency of
the motor? (Estimate g as 10 m/s2.)

a) 2.3%
b) 11%
c) 32%
d) 43%