In this task, you need to count the number of times the given letter appears in the given sentence.

Sentence: 'a small boy in a high chair eating a cupcake'. Find frequency of the letter 'i'
4

Sentence: 'two young ladies that are dancing in the room together'. Find frequency of the letter 'a'
4

Sentence: 'two cows in a pen eat hay on a farm'. Find frequency of the letter 'w'

2