The worksheet Items contains a list of items. For each item, it lists the unit price and a discount percentage that customers get if they purchase at least a minimum quantity of the item. For example, the discount for the first product is $5\%,$ and it is obtained if at least $20$ units are purchased.

Write a sub that asks for an item code with an input box. It should then ask for the number of units purchased, which must be a positive number. $($Make sure that you write code to handle possible system errors due to incorrect inputs from the user$).$ Finally, it should display a message like the following: $$You purchased XXX units of item XXX$.$ The total cost is XXX$.$ Because you purchased at least XXXX units, you got a discount of XXXX on each unit.$$ The last sentence should not be displayed if the user didn$$t purchase enough units to get a discount.

Make sure the sub works even if the data changes, including the possibility of more or fewer items.