This is a semicircle atop a rectangle. The length of the base and dotted side of the rectangle (length b) is needed as well as the height (h) of the rectangle. The radius r of the semicircle is half the base of the rectangle (r=b/2). The area of a circle is πr2, so the area of the semicircle is πr2/2 and the area of the rectangle is bh, so the total area is bh+π(b/2)2/2=bh+πb2/8.