The Baldwin family walked four over five of a mile in four over nine of an hour. What is their unit rate in miles per hour?

four-ninths over four-fifths equals four over nine mile per hour
four-fifths over four-ninths equals one and four-fifths miles per hour
four-ninths over four-fifths equals one and four-fifths miles per hour
four-fifths over four-ninths equals four over nine mile per hour