Woodworkers Laura and Philip make precision pieces for toys. Each toy requires four 8-inch-long sticks. Laura cuts four sticks one at a time, and their lengths are independent. Laura's sticks have mean length 8 inches with a standard deviation 0.15 inches. Philip clamps four sticks together and cuts them all at once so that they all have the same length. Philip's sticks also have a mean length of 8 inches with a standard deviation of 0.15 inches.

a. Laura's four sticks are laid end-to-end. What is the mean of the total length? What is the standard deviation of the total length?

b. Philip's four sticks are laid end-to-end. What is the mean of the total length? What is the standard deviation of the total length?

c. Four sticks, two from Laura and two from Philip, are laid end-to-end. What is the mean of the total length? What is the standard deviation of the total length?