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

[EX Q]: Sentence: 'two people and two children walking in a building'. Find frequency of the letter 'd'
[EX A]: 3

[EX Q]: Sentence: 'three people are gathered around sitting on a park bench'. Find frequency of the letter 'g'
[EX A]: 2

[EX Q]: Sentence: 'a man watches as a fellow surfer catches a wave'. Find frequency of the letter 'u'
[EX A]:
1