With the help of a graph and example(s), explain the concept of semi-variable (or mixed) cost.

Semi-variable cost, also known as mixed cost, is a type of cost that has both fixed and variable components. This means that part of the cost is constant, regardless of the level of activity, while the other part changes in proportion to the level of activity.

Let's take an example of a telephone bill. A telephone bill often has a fixed monthly charge (the fixed cost component) and a variable charge based on the number of minutes used (the variable cost component). So, even if you don't make any calls in a month, you will still have to pay the fixed monthly charge. However, the more calls you make, the higher your bill will be due to the variable charge.

Now, let's represent this concept with a graph:

1. On the x-axis, we have the level of activity (in this case, the number of minutes used).
2. On the y-axis, we have the total cost (in this case, the total telephone bill).

The graph starts at the point that represents the fixed cost (the monthly charge you have to pay regardless of your usage). This is a horizontal line because the fixed cost doesn't change with the level of activity.

Then, there's a line that starts from the end of the fixed cost line and slopes upwards. This line represents the variable cost, which increases as the level of activity increases. The steeper the slope, the higher the variable cost per unit of activity.

The total cost is represented by a line that starts at the same point as the fixed cost line and follows the same slope as the variable cost line. This line shows how the total cost increases as the level of activity increases, taking into account both the fixed and variable costs.

In conclusion, a semi-variable cost has a fixed component that has to be paid regardless of the level of activity, and a variable component that changes in proportion to the level of activity. This concept is important in cost accounting and financial analysis, as it helps businesses predict their costs and make informed decisions.