What is the next number?

𝐟𝐢𝐟𝐭𝐲, 𝐬𝐢𝐱𝐭𝐲, 𝐬𝐞𝐯𝐞𝐧𝐭𝐲, 𝐞𝐢𝐠𝐡𝐭𝐲, ...

• ninety
• forty
• thirty