Mariposa, our recruitment officers told us that we should call them if we haven't heard back from them after 6 weeks.
Audrey Kim, yes there is an essay question. Ours was to describe a mistake we made at work and what we learned from it.
My advice is to power through the multiple choice as best you can to make sure you leave enough time for the essay. It needs to be about a page and a half; if you're worried about your essay writing skills, practice before you go.