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

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

[EX Q]: Sentence: 'a baseball themed birthday cake is on a serving tray'. Find frequency of the letter 'g'
[EX A]: 1

[EX Q]: Sentence: 'a siamese cat kissing itself in front of a mirror'. Find frequency of the letter 'm'
[EX A]:
2