An evergreen nursery usually sells a certain type of shrub after 6 years of growth and shaping. The growth rate during those 6 years is approximated by dh/dt = 1.5t + 5,
where t is the time in years and h is the height in centimeters. The seedlings are 12 centimeters tall when planted (t = 0).
(a) Find the height after t years.
(b) How tall are the shrubs when they are sold?