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

Sentence: 'a man and a woman are walking down the street with an umbrella over their heads'. Find frequency of the letter 'w'
4

Sentence: 'young girl playing with refrigerator magnet while kneeling on floor'. Find frequency of the letter 'n'
6

Sentence: 'a group of three elephants standing next to each other'. Find frequency of the letter 'h'

4