Weather Surface of a conical roof

A cylindrical tower 30ft in diameter has a conical roof the length of whose eaves is 2ft. An element of the roof is inclined 45 degrees to the horizontal. Find the weather surface (see figure).

http://dl.dropbox.com/u/27033827/DSC04813.JPG

Answer at the back of the book: **61.061 square yards.**

what i did was,

i got the radius (2+30)/2

i used cosine function to get the slant height,

i used the radius to get the circumference,

then i got the lateral area of the cone by using LA=1/2(circumference)(slant height)

the answer is on the unit square feet. so i divided the answer by 3 so that i can get square yards. my answer is very far from the answer on the book.

i don't know what i did wrong. or is the book wrong? couldn't be.