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

[EX Q]: Sentence: 'two men with colorful ties are posing for a picture'. Find frequency of the letter 'r'
[EX A]: 4

[EX Q]: Sentence: 'many white birds flying above a river that flows in front of a forest'. Find frequency of the letter 'a'
[EX A]: 5

[EX Q]: Sentence: 'pedestrian sign and bus sign in urban area'. Find frequency of the letter 'g'
[EX A]:
2