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

Sentence: 'a herd of zebra standing on top  of a grass covered field'. Find frequency of the letter 'e'
5

Sentence: 'a batter, catcher and umpire waiting for the pitch and a major league baseball game'. Find frequency of the letter 'c'
3

Sentence: 'a surfer in a wet suit and yellow board is surfing'. Find frequency of the letter 't'

2