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

[EX Q]: Sentence: 'a man standing on a tennis court holding a racquet'. Find frequency of the letter 's'
[EX A]: 2

[EX Q]: Sentence: 'a truck is parked in front of a store'. Find frequency of the letter 't'
[EX A]: 3

[EX Q]: Sentence: 'a red fire hydrant is sitting outside by a curb'. Find frequency of the letter 'd'
[EX A]:
3