Salesforce Exam Sharing-and-Visibility-Designer Topic 9 Question 25 Discussion

The Collections department at Universal Containers uses Salesforce to track its efforts. All Invoices and Invoice Line Items are stored in Salesforce. Invoice Line Item object details, such as Quantity and Extended Amount, should be summarized at the Invoice Object level, and all users who can see a given invoice should always see all invoice line items. Without leveraging Apex code, how should an Architect create the relationship between the Invoice object and the Invoice Line Item Object?