An economic activity is any action that involves the production, distribution, exchange, or consumption of goods and services. It is an activity undertaken to earn a livelihood or to satisfy human wants.
The key characteristics of an economic activity are: \[\begin{array}{rl} \bullet & \text{It involves the use of scarce resources (like land, labor, capital).} \\ \bullet & \text{It is undertaken with an economic motive, i.e., to generate income or wealth.} \\ \bullet & \text{It results in the creation of goods or services that have value and can satisfy human needs.} \\ \end{array}\] Economic activities are broadly classified into three sectors:
\[\begin{array}{rl} 1. & \text{Primary Sector: Activities that involve the direct extraction of natural resources. Examples include farming, mining, fishing, and forestry.} \\ 2. & \text{Secondary Sector: Activities that transform raw materials into finished goods. Examples include manufacturing, construction, and food processing.} \\ 3. & \text{Tertiary Sector: Activities that involve providing services. Examples include transportation, banking, teaching, and healthcare.} \\ \end{array}\]
The table shows the data of running a machine for five years. The original machine cost is Rupees 70,000. In order to minimize the average total cost per year for running the machine, the machine should be replaced after ............. years. (Answer in integer) 