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

[Q]: Sentence: 'two people wearing snowboards sitting on a snowy slope'. Find frequency of the letter 's'
[A]: 5

[Q]: Sentence: 'two giraffes standing next to some trees'. Find frequency of the letter 'f'
[A]: 2

[Q]: Sentence: 'a couple of people on a beach with a surfboard'. Find frequency of the letter 'l'
[A]:
2