MR of n the unit is given by: TRn - TRn-1

Explanation:
- The marginal revenue (MR) is the change in total revenue (TR) that results from producing one additional unit of a good or service.
- In this case, we are considering the MR of the nth unit.
- Total revenue is the total amount of money received from selling a given quantity of a good or service.
- To calculate the MR of the nth unit, we need to find the difference between the total revenue of producing n units and the total revenue of producing n-1 units.
- This can be expressed as: MRn = TRn - TRn-1

Example:
- Let's say a company sells widgets and the total revenue from selling 10 widgets is $1000 and the total revenue from selling 9 widgets is $900.
- To find the MR of the 10th widget, we subtract the total revenue of selling 9 widgets from the total revenue of selling 10 widgets: MR10 = TR10 - TR9 = $1000 - $900 = $100.

Significance:
- The MR of a unit helps businesses determine how much additional revenue they can expect to generate by producing one more unit of a good or service.
- If the MR of a unit is positive, it means that producing one more unit will increase total revenue.
- If the MR of a unit is negative, it means that producing one more unit will decrease total revenue.
- By analyzing the MR of each unit, businesses can make informed decisions about production levels and pricing strategies to maximize their profits.

Conclusion:
- The correct answer is option 'C' TRn - TRn-1, which represents the calculation for marginal revenue of the nth unit.