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

[EX Q]: Sentence: 'a black bear sitting in the grass taking a rest'. Find frequency of the letter 'a'
[EX A]: 6

[EX Q]: Sentence: 'young girl playing with refrigerator magnet while kneeling on floor'. Find frequency of the letter 'n'
[EX A]: 6

[EX Q]: Sentence: 'a man is taking a mirror image of himself'. Find frequency of the letter 't'
[EX A]:
1