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

Ex Input:
Sentence: 'a blue fire hydrant painted on the bottom of it'. Find frequency of the letter 'h'

Ex Output:
2

Ex Input:
Sentence: 'hotel towels with sunglasses perched and hotel business cards and catalog'. Find frequency of the letter 'o'

Ex Output:
4

Ex Input:
Sentence: 'church tower, beige stone color under partly cloudy skies'. Find frequency of the letter 'u'

Ex Output:
3