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

Ex Input:
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 Output:
9

Ex Input:
Sentence: 'a woman in a tank top reaches out for a frisbee'. Find frequency of the letter 'a'

Ex Output:
6

Ex Input:
Sentence: 'a young man riding a skateboard in a skate park'. Find frequency of the letter 'g'

Ex Output:
2