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

Sentence: 'a bird is standing on the ledge of the building'. Find frequency of the letter 't'
3

Sentence: 'a line of people on motorcycles on the road'. Find frequency of the letter 'e'
5

Sentence: 'a boat tied to a dock in the sea having a large dog on board'. Find frequency of the letter 'd'

4