Minimum taxable limit of camels

1918. Camel has 12 minimum taxable limits:

1.5 camels: and the Zakat on them is one sheep. As long as the number of camels does not reach five, no Zakat is payable on them.
2.10 camels: and the Zakat on them is 2 sheep.
3.15 camels: and the Zakat on them is 3 sheep.
4.20 camels: and the Zakat on them is 4 sheep.
5.25 camels: and the Zakat on them is 5 sheep.