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

[Q]: Sentence: 'a person riding a skate board on a city street'. Find frequency of the letter 'a'
[A]: 5


[Q]: Sentence: 'a person is holding a chocolate doughnut with rainbow sprinkles'. Find frequency of the letter 's'
[A]: 4


[Q]: Sentence: 'a man smiles and holds a hot dog with lots of toppings'. Find frequency of the letter 'o'
[A]:
6