Given the fixed cost $b = 1800$ dollars and the variable cost per bicycle $m = 80$ dollars, the cost function can be written as:

$C(x) = 80x + 1800$

Here, $C(x)$ represents the total cost of manufacturing $x$ bicycles in a day.

Would you like more details or have any questions about this?

Here are 5 related questions that expand on this topic:

1. How would the cost function change if the variable cost per bicycle increased to $100?
2. What does the slope of the cost function indicate in terms of production costs?
3. How would you find the total cost for manufacturing 50 bicycles in one day using this cost function?
4. How can you determine the number of bicycles that need to be manufactured for the total cost to reach $5000?
5. How does the cost function change if the fixed cost increases by $500?

Tip: Understanding the components of a cost function helps in budgeting and pricing decisions in a business.