The probability of Yazhini understanding Bayes' Theorem

The probability of Swetha and Yazhini buying some snack-gift for Jayashree are 0.8 and 0.6 respectively. The probability of Swetha buying her an apple cake is 0.1 and the probability of Yazhini doing so is 0.01. What is the probability that Yazhini has bought Jayashree an apple cake given that the latter is enjoying one?

I came up with this question to annoy Jayashree (who obviously loves apple cakes, which the rest of us hate) on her birthday.

She decided to change all the values to 1.0 to "make the calculations easy"

I'm tempted to change P(A|Y) to 0.0.

Update 9/5/2024: Yazhini got Jayashree a single apple cake. The idiot devoured it happily.

Videos that helped me wrap my head around Bayes' Theorem: