8. A manufacturing plant has the following short-run cost function:

[tex]\[ C(q) = 100q - 2q^2 + 0.5q^3 + 45 \][/tex]

Determine the following functions:

A. The total fixed cost (TFC) and total variable cost (TVC).

B. Average fixed cost (AFC) and average variable cost (AVC).

C. Average cost (AC) and marginal cost (MC).

D. Draw the total fixed cost (TFC), total variable cost (TVC), and total cost (TC) curves of the function.



Answer :

Let's break down the given cost function [tex]\(C(q) = 100q - 2q^2 + 0.5q^3 + 45\)[/tex] step by step.

### Part A: Total Fixed Cost (TFC) and Total Variable Cost (TVC)

Total Fixed Cost (TFC):
The Total Fixed Cost is the portion of the cost that does not change with the output quantity [tex]\(q\)[/tex]. From the given cost function, the constant term "45" represents the Total Fixed Cost.
[tex]\[ \text{TFC} = 45 \][/tex]

Total Variable Cost (TVC):
The Total Variable Cost is the portion of the cost that changes with the output quantity [tex]\(q\)[/tex]. We subtract the TFC from the total cost function to derive the TVC.
[tex]\[ \text{TVC} = 100q - 2q^2 + 0.5q^3 \][/tex]

### Part B: Average Fixed Cost (AFC) and Average Variable Cost (AVC)

Average Fixed Cost (AFC):
The Average Fixed Cost is the Total Fixed Cost divided by the output quantity [tex]\(q\)[/tex].
[tex]\[ \text{AFC} = \frac{TFC}{q} = \frac{45}{q} \][/tex]

Average Variable Cost (AVC):
The Average Variable Cost is the Total Variable Cost divided by the output quantity [tex]\(q\)[/tex].
[tex]\[ \text{AVC} = \frac{TVC}{q} = \frac{100q - 2q^2 + 0.5q^3}{q} = 100 - 2q + 0.5q^2 \][/tex]

### Part C: Average Cost (AC) and Marginal Cost (MC)

Average Cost (AC):
The Average Cost is the total cost (which is the sum of TFC and TVC) divided by the output quantity [tex]\(q\)[/tex].
[tex]\[ \text{AC} = \frac{C(q)}{q} = \frac{100q - 2q^2 + 0.5q^3 + 45}{q} = 100 - 2q + 0.5q^2 + \frac{45}{q} \][/tex]

Marginal Cost (MC):
The Marginal Cost is the derivative of the total cost function with respect to quantity [tex]\(q\)[/tex].
[tex]\[ \text{MC} = \frac{dC(q)}{dq} = 100 - 4q + 1.5q^2 \][/tex]

### Part D: Graphical Representation

To draw the Total Fixed Cost (TFC), Total Variable Cost (TVC), and Total Cost (TC) curves:

1. TFC Curve: This will be a horizontal line at the value 45 on the cost-axis, as TFC is constant regardless of output quantity [tex]\( q \)[/tex].

2. TVC Curve: This curve represents the function [tex]\( 100q - 2q^2 + 0.5q^3 \)[/tex]. It starts from the origin and will increase as [tex]\( q \)[/tex] increases.

3. TC Curve: This is the sum of TFC and TVC. Thus,
[tex]\[ \text{TC} = \text{TFC} + \text{TVC} = 45 + 100q - 2q^2 + 0.5q^3 \][/tex]
Therefore, the TC curve is another cubic function that starts at 45 when [tex]\( q = 0 \)[/tex] and increases as [tex]\( q \)[/tex] increases.

To visualize these functions, you would plot them on a graph with quantity [tex]\( q \)[/tex] on the x-axis and cost on the y-axis.

- TFC will be a horizontal line.
- TVC and TC will start from the origin and 45 respectively and exhibit cubic growth patterns.

I hope this comprehensive step-by-step breakdown clarifies each part of the question!