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

[EX Q]: Sentence: 'a train going over a bridge with some buildings in the background'. Find frequency of the letter 'd'
[EX A]: 3

[EX Q]: Sentence: 'a double decker transit bus parks by a blue on the side of the street in front of a brick building in the city'. Find frequency of the letter 't'
[EX A]: 9

[EX Q]: Sentence: 'a very open  mostly white room in a house'. Find frequency of the letter 'h'
[EX A]:
2