hiding/unhiding rows based on a selection from a drop down

Hi,

I'm trying to formulate a spreadsheet that will hide/unhide rows depending on a selection made in a drop down (list). There are 3 options in the drop down that correlate to a type of request; whichever option is selected needs to only show the relevent rows for that type. I've listed a reference in column A for each row that would need to show for the specific type of request. I'm not very good with macros but I think there might be a way to accomplish this. I've attached the document; any help would be appriciated.

Thanks!