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

[EX Q]: Sentence: 'a guy surfs a wave with his surfboard'. Find frequency of the letter 's'
[EX A]: 4

[EX Q]: Sentence: 'there is an old stove with old pots on the burners'. Find frequency of the letter 't'
[EX A]: 5

[EX Q]: Sentence: 'a surfer is in the middle of an ocean wave'. Find frequency of the letter 'i'
[EX A]:
3