import Data.Array
import Data.Ratio
import qualified Data.IntMap as IM
import Control.Monad (liftM, forM_)
import Text.Printf

fact :: Integer -> Integer
fact n
  | n <= 1 = 1
  | otherwise = n * fact (n-1)

comb :: Integer -> Integer -> Integer
comb m n | m < n = 0
comb m n = product [m,m-1..(n+1)] `div` fact (m-n)

f :: Integer -> Integer -> Rational
f c n = table ! 0
  where
    allc = comb c n
    table = array (0,c) [(i, g i) | i<-[0..c]]
    g cur
      | cur==c = 0
      | otherwise = r / (1-r) + x / (1-r)
         where
           r = comb cur n % allc
           x = sum $ do
                 let remain = c - cur
                 new <- [1 .. min n remain]
                 let count = (table ! (cur+new)) + 1
                 return $ (comb remain new * comb cur (n-new) % allc) * count

main :: IO ()
main = do
  n <- liftM read getLine
  forM_ [(1::Int)..n] $ \i -> do
    [c,n] <- liftM (map read . words) getLine
    printf "Case #%d: %.7f\n" i (fromRational (f c n) :: Double)