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

[Q]: Sentence: 'a woman is looking at sheep off in a field'. Find frequency of the letter 'm'
[A]: 1


[Q]: Sentence: 'an area that has surrounded by a metal fence'. Find frequency of the letter 'o'
[A]: 1


[Q]: Sentence: 'a shower with a window a vanity and a mirror'. Find frequency of the letter 'r'
[A]:
4