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

Sentence: 'a tennis player that is running to get the tennis ball'. Find frequency of the letter 't'
7

Sentence: 'a young girl skiing down a snowy mountain'. Find frequency of the letter 'l'
1

Sentence: 'a man is standing on a pier before a calm lake'. Find frequency of the letter 'd'

1