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

Input: Consider Input: Sentence: 'a castle like bed room that has the era of templar knight similarities'. Find frequency of the letter 'm'

Output: 3

Input: Consider Input: Sentence: 'a man hitting a tennis ball with a tennis racquet'. Find frequency of the letter 't'

Output: 6

Input: Consider Input: Sentence: 'a dog as seen in a rear view mirror of a vehicle'. Find frequency of the letter 's'
Output: 2