From the graph,
We can observe that it is a linear graph. In a line graph, independent variable is represented on the X-axis and dependent variable on the Y-axis. So, our independent and dependent variables are no. of items sold and profit earned respectively. The question says, what is the profit earned when no. of items sold is 350?
As we can spot in the graph that 350 lies exactly between 300 and 400. The profit earned should also lie exactly between 1500 and 2000 because it is a linear graph. The no. that lies between 1500 and 2000 is 1500+20002 = 1750.
So the profit earned when no. of items sold is 350 is Rs. 1750.