The periodic review inventory model operates using two model parameters, TI (target inventory) and RP (review period). These two parameters are: Select one: O a. TI, which represents a fixed order quantity and RP, which represents a variable reorder point quantity of inventory. O b. TI, which represents a variable order quantity and RP, which represents a variable reorder point quantity of inventory. O c. TI, which represents a variable quantity of units one would order up to and RP, which represents a fixed amount of time between orders. O d. TI, which represents a fixed quantity of units one would order up to and RP, which represents a fixed amount of time between orders. O e. Ti, which represents a fixed quantity of units one would order up to and RP, which represents a variable amount of time between orders