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

Sentence: 'a half eaten doughnut in a persons hand'. Find frequency of the letter 'h'
3

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: 'a baseball player holding a bat standing next to a base'. Find frequency of the letter 'g'

2