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

Sentence: 'a woman in yellow dress standing next to a horse'. Find frequency of the letter 'l'
2

Sentence: 'a player swings his bat at a baseball game'. Find frequency of the letter 'p'
1

Sentence: 'a tennis racket laying by a tennis ball on the grassy ground'. Find frequency of the letter 'o'

2