Final answer:
The price change of Car B was the greatest at £40.
Step-by-step explanation:
In order to determine which car's price changed by the greatest amount, we need to calculate the difference between the rounded prices for each car. The rounded prices are as follows:
- Car A: £12,400
 - Car B: £16,800
 - Car C: £14,600
 
Now, we can calculate the differences:
- Car A: £12,400 - £12,380 = £20
 - Car B: £16,800 - £16,760 = £40
 - Car C: £14,600 - £14,580 = £20
 
Therefore, we can see that Car B had the greatest price change, as its price increased by £40.