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

[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 group of men standing on the side of a boat'. Find frequency of the letter 'o'
[EX A]: 5

[EX Q]: Sentence: 'some baseball players are playing baseball on a field'. Find frequency of the letter 'l'
[EX A]:
7