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

[EX Q]: Sentence: 'a number of small boats on a beach near an umbrella'. Find frequency of the letter 's'
[EX A]: 2

[EX Q]: Sentence: 'a microwave oven with a yellow note on the door'. Find frequency of the letter 'w'
[EX A]: 3

[EX Q]: Sentence: 'apartment building with fire escapes and red traffic light'. Find frequency of the letter 'n'
[EX A]:
3