When a sales rep picks a button on an opportunity, a simple discount calculator screen should be launched. Which automation tool should an administrator use to build this discount calculator screen?

Process Builder is used for behind-the-scenes automation based on record changes or platform events and cannot create user-facing screens for interaction.

Platform Events are used for publishing and subscribing to event messages and are not a tool for building interactive user screens.

Workflow Rules are an older automation tool primarily used for field updates, email alerts, tasks, and outbound messages, and cannot create interactive screen-based calculators.

Flow Builder, specifically a Screen Flow, is the appropriate automation tool to build a custom user interface (a screen) that can accept input (like discount parameters) and perform calculations, which can then be launched from a button or link on an opportunity record.