Describe Kant's line of reasoning in which he arrives at the Categorical Imperative. What does this imply that all agents must have access to?

Describe Kant's line of reasoning in which he arrives at the Categorical Imperative. What does this imply that all agents must have access to? Is this a reasonable constraint on moral agency and moral decision making? Additionally consider the Case of the Inquiring Murder once more. Provide a scenario in which it would be in accordance with laws of your country to tell the Inquiring Murder which way the victim went. Describe how this might be in accordance with the Categorical Imperative.