The problem you're presenting shows a cost function and asks for the calculation of different types of costs related to production. The given total cost (TC) function is:

$TC = 20Q + 45$

Here, $Q$ represents the quantity of goods produced.

Let’s break down the different components and determine the answers for each part:

a) Fixed Cost (FC):

The fixed cost is the portion of the total cost that does not depend on the quantity produced. In the equation $TC = 20Q + 45$, the fixed cost is the constant term, which is 45.

$FC = 45$

b) Variable Cost (VC):

The variable cost is the part of the total cost that changes with the level of output. The term involving $Q$, which is $20Q$, represents the variable cost.

$VC = 20Q$

c) Average Variable Cost (AVC):

The average variable cost is the variable cost per unit of output, calculated by dividing the variable cost by the quantity $Q$.

$AVC = \frac{VC}{Q} = \frac{20Q}{Q} = 20$

d) Average Cost (AC):

The average cost is the total cost per unit of output, calculated by dividing the total cost by the quantity $Q$.

$AC = \frac{TC}{Q} = \frac{20Q + 45}{Q} = 20 + \frac{45}{Q}$

This provides the breakdown of costs as requested.

Would you like further details or clarification on any of the steps? Here are five related questions to expand on this:

1. What is the relationship between marginal cost and variable cost?
2. How does fixed cost behave as output increases?
3. What happens to average cost as production increases indefinitely?
4. Can the average variable cost ever exceed the average cost? Why or why not?
5. How can you determine marginal cost from the total cost function?

Tip: Always separate fixed and variable costs to clearly see how they influence overall expenses at different output levels.