import Control.Monad
import Text.Printf

main :: IO ()
main = do
  t <- readLn
  forM_ [(1::Int)..t] $ \i -> do
    [a,b] <- liftM (map read . words) getLine
    ps <- liftM (map read . words) getLine
    let ans = solve b ps
    printf "Case #%d: %f\n" i ans

solve :: Int -> [Double] -> Double
solve b ps = minimum $ opt3 : (opt2 (reverse ps) (length ps) (product ps) 0)
  where
    opt3 = fromIntegral $ 1 + b + 1

    opt2 :: [Double] -> Int -> Double -> Int -> [Double]
    opt2 [] _ _ keys = return $ fromIntegral (keys + b + 1)
    opt2 pps@(p:ps) len pp keys =
      fromIntegral (keys + (b - len) + 1) + (1 - pp) * fromIntegral (b + 1) :
      opt2 ps (len - 1) (pp / p) (keys + 1)