Final answer:
The probability density function (PDF) for the battery recharging time is a uniform distribution over the interval [100, 140]. The PDF, f(x), is equal to 1/40 within this interval.
Step-by-step explanation:
The probability density function (PDF) for the battery recharging time can be defined as a uniform distribution over the interval [100, 140].
This means that any value within this interval has an equal chance of being the actual recharging time required.
Mathematically, the PDF, f(x), is given by:
f(x) = 1 / (140 - 100) = 1 / 40, for 100 <= x <= 140