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: 'a grapefruit, toast, coffee and other items are on a tray'. Find frequency of the letter 't'
6

Sentence: 'a man in a chef's outfit holding a knife while in a kitchen'. Find frequency of the letter 'm'
1