Final answer:
Jakob will need to use a Text Box control to display the value of the total inventory by multiplying the ItemsOnHand by the ItemCost.
Step-by-step explanation:
To present the value of the total inventory for a given product by multiplying the value in the ItemsOnHand field by the ItemCost value, Jakob will need to use a Text Box control. A Text Box allows for the display of calculated values, which can be updated dynamically based on other values or inputs within the report. Labels are static and won't allow for calculations. Buttons are for triggering actions, not displaying values. Combo Boxes are used for selecting items from a list, not for calculations.