The quantity demanded per month, x, of a certain make of tablet computer is related to the average unit price, p (in dollars), of tablet computers by the equation x = f(p) = (100/9) √(810,000 − p²).
It is estimated that t months from now, the average price of a tablet computer will be given by p(t) = 400/(1 + 1/8√t) + 200, (0 ≤ t ≤ 60)
dollars.
Find the rate at which the quantity demanded per month of the tablet computers will be changing 49 months from now. (Round your answer to one decimal place.)