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

[Q]: Sentence: 'a man and several white red and blue airplanes'. Find frequency of the letter 'u'
[A]: 1


[Q]: Sentence: 'a toasted sub sandwich is next to a salad'. Find frequency of the letter 'a'
[A]: 6


[Q]: Sentence: 'a black and white toilet sitting in a bathroom next to a plant filled with waste'. Find frequency of the letter 'a'
[A]:
8