Work can be calculated using the formula:
\[ \text{Work} = \text{Force} \times \text{Distance} \times \cos(\theta) \]
In this case, the force is the weight of the box (72 N), the distance is the height it is lifted (0.9 m), and since the force is applied vertically upwards and the distance is also in the vertical direction, \(\theta = 0^\circ\) (which means \(\cos(0^\circ) = 1\)).
Thus, the calculation simplifies to:
\[ \text{Work} = \text{Force} \times \text{Distance} \]
Now substituting the values:
\[ \text{Work} = 72 , \text{N} \times 0.9 , \text{m} \]
Calculating:
\[ \text{Work} = 64.8 , \text{J} \]
Thus, the mail carrier did 64.8 J of work.
The correct answer is: 64.8 J.