[tex]\sf\ The\ area\ of\ the\ bookmark\ is\ the\ area\ of\ the\ rectangle\ plus\ the\ area\ of\\the\ circle\ (two\ semi-circles\ make\ one\ circle).\\\\The\ area\ of\ the\ rectangle:\\12\times4=48\ cm\\\\The\ area\ of\ the\ two\ semicircles:\\\pi r^2=\\\pi 2^2=\\4\pi\ cm\\The\ width\ of\ the\ rectangle\ was\ the\ diameter\ of\ the\ cirlce.\ So\ the\ radius\\ was\ half\ the\ diameter\ or\ 2.\\\\The\ area\ of\ the\ bookmark:\\{\boxed{48\ cm+4\pi\ cm}[/tex]