A model for the average price of a pound of white sugar in a certain country from August 1993 to August 2003 is given by the function S(t) = −0.00003237t5 + 0.0009037t4 − 0.008956t3 + 0.03629t2 − 0.04577t + 0.3932
where t is measured in years since August of 1993. Estimate the times when sugar was cheapest and most expensive during the period 1993-2003. (Round your answers to three decimal places.)