A concrete delivery truck shuttles between a concrete mixing plant and a construction site for the entire 10-h working day. The one-way trip takes on the average 1 h with a standard deviation of 0.2 h. Assuming that the travel time can be modeled by a normal distribution, what is the probability of completing a two-way (complete) trip within 1.5 h? Assuming that the time needed to unload the truck is also a normal variate with a mean of 0.5 h and standard deviation of 0.2 h, what are the mean and standard deviation of the time required for a complete two-way trip with unloading?