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

Sentence: 'a small boat travels on the water next to the shore'. Find frequency of the letter 'a'
5

Sentence: 'silhouette of person playing frisbee with moutain and sunset'. Find frequency of the letter 'i'
5

Sentence: 'a commuter train travels past an empty train station'. Find frequency of the letter 'l'

1

