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

Sentence: 'the counter of a doctor's office, including a laptop, cotton swabs, and tongue depressors'. Find frequency of the letter 'g'
2

Sentence: 'man sitting on the side of a van playing the guitar'. Find frequency of the letter 'm'
1

Sentence: 'man sitting on a train typing on his laptop'. Find frequency of the letter 'o'

3

