The sales S (in thousands of units) of a seasonal product are given by the model below, where t is the time in months, with t-1 corresponding to January. Find the average sales for each time period. (Round your answers to two decimal places.) s-74.5543.94 sin It 6 sin (a) The first quarter (O sts 3) thousand units (b) The second quarter (3 s ts 6) thousand units (c) The entire year (0štš12) thousand units