Study the following graph and answer the question that follows.
In 2021, the production of wheat increased over 2020 by the same percentage as that in 2020 over 2018 and the production of rice increased by 30% over 2020. The difference (in million tonnes) between the productions of wheat and rice in 2021 was:
1
18.5
2
15
3
18
4
16.5