﻿How do firms choose a technology? Of course they first look at the available technologies and choose the one that costs the least and produce the same quality products. As before, let's assume we're a textile firm and we want to produce 100 meters of cloth, and we want to work out the cost of technology P1 for our firm. This technology is relatively energy-intensive because it requires three tons of coal and two workers. Now, how do we calculate the cost of this? It all depends on two pieces of information: the cost of labor for us and the cost of coal. Let's assume the cost of labor is £10 per hour - the wage is £10 per hour, and the cost of coal is £20 per ton. Now, given this information, let's calculate the total cost of technology P1. We're going to require two workers, so two multiplied by £10 per hour. Then we're going to need three tons of coal so three multiplied by £20. Overall we get £80 for the total cost of technology P1. So, let's assume there's another available technology for our firm, P2, and this is a relatively labor-intensive technology because you're going to need six workers and only one ton of coal to produce 100 meters of cloth. Now let's work out the cost of this technology. You're going to be needing six workers, so that is six multiplied by £10 per hour, and you're going to need only one ton of gold - that's one multiplied by £20, and then you still get £80, the total cost of this technology. Now that P1 and P2 cost the same we can actually draw a line between them, and call this an isocost line. Whatever exists on this line, costs the same for our firm and that is £80, so our firm would be indifferent between choosing P2 or P1 or any other technology that may exist on this line. Now technology Q1 and Q2 lie at a higher iso cost curve. There are more costly technologies obviously, why? Because, for instance, if you compare Q1 to P1, Q1 uses more of the both inputs - more worker and more coal, so therefore it's definitely more costly. Same with the Q2 - if you compare Q2 with P1. Now you might ask: what about technology Q3 here? Yes, this technology is using less coal but much much more workers, so the total cost of this technology is still higher than P1 and P2. Let's add more isocost lines. This line is under £420, this one is \$40. As you can see anything to the right of this line costs more than £80, anything on the left costs less than that, so as a firm we would like to choose technologies that are at the lowest isocost curves. For instance, in this case £40, however, we don't have any technologies there, those technologies have not been invented yet, the available technologies that are cheapest are P1 and P2. Now, let me add one final thing. The slope of these curves are the same, and that is the price of labor over the price of coal, that is wage £10 over the price of coal £20 per ton, that is one over two. We express it in minus terms because the slope of the curves is downward - this slope means that to use one extra ton of coal our firm needs to give up two of its workers in order to keep the total cost of its production the same. Let me give you an example. Let's assume our firm is now producing a technology F. It's using 12 workers and no energy. Now it wants to move to technology G. It has to consume one extra ton of coal but for that it needs to give up two of its workers in order to keep the total cost of its production the same. Thank you.