Based on data about the growth of a variety of ornamental cherry trees, the following logarithmic model about these trees was determined: h(t) = 6.108 ln(t) + 6.099, where t = age of tree in years and h (t) = height of tree, in feet. Note that "ln" refers to the natural log function. Use this model to answer the following questions. Show work.
(a) At age 4 years, how tall is this type of ornamental cherry tree, to the nearest tenth of a foot?
(b) How long will it take for an ornamental cherry tree to reach a height of 20 feet? Your answer should be to the neareset tenth of a year.