(a) The arc length of each of the two smaller semicircles is
, and the arc length of each of the two larger semicircles is
. Therefore, the perimeter is
.
(b) The area of each of the smaller semicircles is
, and the areaof each of the larger semicircles is
.
So, the combined areas of the four semicircles is
.
The area of the rectangle is 60, so the total area is
.