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

[Q]: Sentence: 'some cubbies with towels in a blue bathroom'. Find frequency of the letter 'l'
[A]: 2

[Q]: Sentence: 'a girl sits on a surfboard and smiles'. Find frequency of the letter 'i'
[A]: 3

[Q]: Sentence: 'a herd of zebra standing on top of a grass covered field'. Find frequency of the letter 'e'
[A]:
5