The is a period of time long enough for firms to alter their plant capacities and for the number of firms in the industry to change.

The long run is a period of time long enough for firms to alter their plant capacities and for the number of firms in the industry to change.

Explanation:

In the business world, the long run is a period of time that is not fixed. In the long run, the firm or manufacturer can change the production rate of a product according to its demand in the market. In this time period, a specific firm or company can either increase its numbers of firms depending on the sales or it can decrease its number of firms or reduce the number of workers if enough sale is not being made.

answer; post closing trial balance;