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

Sentence: 'a stop sign near a rail road crossing sign'. Find frequency of the letter 'g'
3

Sentence: 'a line of people on motorcycles on the road'. Find frequency of the letter 'e'
5

Sentence: 'a young boy holding food in his hands next to apple tree'. Find frequency of the letter 'o'

6