^^^ If you don't want a join in the first piece of carpet above (and that the supplier only sells whole metre lengths), you'll need a 5m length from a 4m wide roll, so (despite the area to be covered actually being under 14 sq m), you'd have to buy 20 sq m of carpet.
The second dimension is annoying awkward too, as the length is just a couple of centimetres over 3m. You might need to buy a 1m piece off a 4m wide roll, making 4 sq m.
Similarly, the fact that 40" is just a centimetre-and-a-bit over 1m makes the last piece tricky too. If you didn't want to join offcuts from the first two bits together, you could end up having to buy 2m off a 2m wide roll, giving you another 4sq m.
That would take your total up to 28 sq m, with a hell of a lot of offcuts left over!
So, as I indicated initially, the problem isn't just one of the total area to be covered. You need to consider whether joins in your carpet are acceptable and, if so, how you're going to be putting your giant jigsaw puzzle together.