Which website citation is correctly formatted according to MLA standards?

MyPlate. United States Department of Agriculture, n.p. Web.
MyPlate. United States Department of Agriculture, 7 June 2013. Web. 30 May 2012.
United States Department of Agriculture. MyPlate. United States Department of Agriculture, 30 May 2012. Web. 7 June 2013.
MyPlate. United States Department of Agriculture, 30 May 2012. Web. 7 June 2013.