Why did the Qur’an use the word "tilkuma" (تلكما) to refer to the tree, even though it is singular, and does "tilkuma" refer to Adam and Eve?

The word "tilkuma" is composed of the demonstrative pronoun "ti" and the attached pronoun (kāf al-khitāb) "kuma." The demonstrative pronoun "ti" refers to the tree (singular feminine), and the attached pronoun "kuma" refers to Adam and Eve (dual).