Twelfth night: Act 2 scene 5

why does fabian not like malvolio? told on him to olivia that he was involved in bearbaiting
what is malvolio doing when he sees the note? talking to himself in the garden (talking of himself proudly)
after reading the note, what does malvolio say? he wil; be count malvolio and call in toby and tell him to stop being a drunken fool
why does maria believe malvolio will think the note is from olivia? she and maria have the same handwriting
what does malvolio believe means him in the letter? MOAI