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

[EX Q]: Sentence: 'a red and white train passing a train station'. Find frequency of the letter 'a'
[EX A]: 7

[EX Q]: Sentence: 'a doll with huge eyes and black hair with blunt bangs holds a red umbrella'. Find frequency of the letter 'e'
[EX A]: 5

[EX Q]: Sentence: 'a person under an umbrella during a rainy day'. Find frequency of the letter 'd'
[EX A]:
3