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

Sentence: 'this is a sign in front of a large cathedral'. Find frequency of the letter 'a'
5

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'
9

Sentence: 'two double decker buses parked by a bike rack'. Find frequency of the letter 't'

1