Riverbed Corp uses a periodic inventory system, Its records show the following for the month of May, in which 75 units were sold. Date May 1 15 Explanation Inventory Purchase Purchase Total Units 34 26 40 100 Unit Cost $8 9 10 Total Cost $272 234 400 $906 24 (a) Calculate the weighted-average unit cost. (Round answer to 3 decimal places, e.g. 5.125.) Weighted average unit cost $ $