To determine the marginal cost of producing the fourth jacket, we need to focus on the definition of marginal cost. Marginal cost is the additional cost incurred to produce one more unit of a good.
In this case, we will look at the cost to produce the total number of jackets just before and just after the fourth jacket.
1. The total cost to produce 3 jackets is given as 43 dollars.
2. The total cost to produce 4 jackets is given as 55 dollars.
The marginal cost is calculated as the difference between the total cost to produce 4 jackets and the total cost to produce 3 jackets:
[tex]\[ \text{Marginal Cost} = \text{Total Cost (4 jackets)} - \text{Total Cost (3 jackets)} \][/tex]
[tex]\[ \text{Marginal Cost} = 55 - 43 \][/tex]
So, the marginal cost to produce the fourth jacket is:
[tex]\[ \text{Marginal Cost} = 12 \][/tex]
Therefore, the correct answer is:
[tex]\[ \boxed{12} \][/tex]
