I$\text{'}$m still trying to learn but I could not understand when time comes in the question. Could you detail more about the what should I do when times come in the question and reasons?

Question $2$:

The probabilities of the numbers of cars that will pass a certain point on the E$6$ in one minute is given

below:

a$)$ What is the standard deviation of the number of cars that will pass this point in the next $8$

minutes?

b$)$ What is the probability that the number of cars that pass this point in the next hour is between

$150$ and $200$ cars $(150$ and $200$ included$)?$

c$)$ What is the variance of the average of the cars that pass this point in one hour $($the unit for the

average is cars per minute$)?$