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

Example Input: Sentence: 'some food on plates next to each other on a table'. Find frequency of the letter 'e'
Example Output: 6

Example Input: Sentence: 'a parking meter painted green with a sign that describes it as not a parking meter'. Find frequency of the letter 's'
Example Output: 4

Example Input: Sentence: 'this photo shows a kitchen with microwave, stove and island'. Find frequency of the letter 'i'
Example Output:
5

