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

Example Input: Sentence: 'a tower with some bright lights and clocks on it'. Find frequency of the letter 'h'
Example Output: 3

Example Input: Sentence: 'a bowl of granola with raspberries and honey on top with a spoon'. Find frequency of the letter 'w'
Example Output: 3

Example Input: Sentence: 'two marine air crafts with people near by'. Find frequency of the letter 'w'
Example Output:
2