Final answer:
The function describing the relationship between net earnings X and self-employment tax Y can't be determined without specific information about the self-employment tax rate. However, the provided information illustrates how economic relationships are modeled as functions, highlighting that the self-employment tax would normally be a function of net earnings.
Step-by-step explanation:
In addressing the question about the function that describes the relationship between X, the amount of net earnings, and Y, the self-employment tax, it is unclear which of the presented options (A, B, C, or D) accurately reflects this relationship without additional context or a specific formula relating X to Y within the context of self-employment tax. However, we can use the provided equations related to economic parameters to understand the concept of function and relationship in an economic model.
For example, the final given formula Y = 3923 indicates that Y, here representing national income, is a constant number in this specific scenario when equilibrium is achieved. This doesn't directly help us find a formula for the self-employment tax, but it does illustrate how a relationship between economic factors can be expressed as a function.
In real-world applications, self-employment tax is typically a percentage of net earnings. If you were to look for a direct relationship, it would tend closer to options like A or C, which are based on a percentage or set addition to X. Since we do not have the exact tax rate or other specific parameters in your question, we cannot provide the exact answer. Hence, to accurately find the function Y = f(X), detailed information regarding the self-employment tax rate applied to net earnings is required.