K A mathematical model for the average of a group of people learning to type is given by N(t) = 7+ Int, t 1, where N(t) is the number of words per minute typed after t hours of instruction and practice (2 hours per day, 5 days per week). What is the rate of learning after 40 hours of instruction and practice? The rate of learning is words/minute per hour. (Type an exact answer.)