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

[Q]: Sentence: 'some sheep are standing in a grassy field'. Find frequency of the letter 'n'
[A]: 3


[Q]: Sentence: 'a boy swinging a bat while playing baseball'. Find frequency of the letter 'h'
[A]: 1


[Q]: Sentence: 'several travelers are moving though a station pathway'. Find frequency of the letter 'a'
[A]:
7