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

[Q]: Sentence: 'a group of cars and house on truck passing in a street'. Find frequency of the letter 'i'
[A]: 2


[Q]: Sentence: 'one woman is arranging the other woman's hair'. Find frequency of the letter 'o'
[A]: 4


[Q]: Sentence: 'a kite is flying in the air at a park'. Find frequency of the letter 'r'
[A]:
2