Well, half-life is the radioactivity of an identified isotope that decreases by half of the actual value.
So, your answer would be C.
What following terms I don’t see any please make your question clear
<span>2700 Joules
The important value here is how high the escalator moved you. The actual length doesn't matter. All it affects is how fast the work is performed upon you. So the escalator lifted 64 kg against gravity for 4.3m. So:
4.3 m * 9.8 m/s^2 * 64 kg = 2696.96 kg*m^2/s^2 = 2696.96 Joules
Rounding to 2 significant figures gives 2700 Joules</span>
