This is the masculine you, isn't it? How would the other form be pronounced? yeshelkhá?
Would someone please explain or point to an explanation for stress in "כמה": I hear both káma and kamá in various places; sometimes both from the same source in different places - it's confusing. AnCatDubh says that kamá is somehow more formal, but that really does not help enough: still can't tell where/when to use one or the other.