The price per square foot in dollars of prime space in a big city from 2004 through 2009 is approximated by the function R(t) = 0.5223 - 4.166t2 + 7.22t + 236.5 (0 s t $ 5) where t is measured in years, with t = 0 corresponding to 2004. (a) When was the office space rent lowest? Round your answer to two decimal places, if necessary. You MUST justify that your result is an optimal value. t = years after 2004 (b) What was the lowest office space rent during the period in question? Round your answer to two decimal places, if necessary. dollars per square foot Complete the following parts. (c) To answer the two questions above, we need the critical numbers of ---Select--- -Select-- (d) These critical numbers are (Enter your answers as R parated list. If an answer does not exist, enter DNE.) R P