propSellQtyMatch :: OrderSell -> Book -> Bool
propSellQtyMatch sell book = bookLiquidity book + sSize sell - (2 * sum (map tradeSize trades)) == bookLiquidity newBook
  where (newBook, trades) = processSell book sell
propSellQtyMatch :: OrderSell -> Book -> Bool
propSellQtyMatch sell book = bookLiquidity book + sSize sell - (2 * sum (map tradeSize trades)) == bookLiquidity newBook
  where (newBook, trades) = processSell book sell
propSellQtyMatch sell book = bookLiquidity book + sSize sell - (2 * sum (map tradeSize trades)) == bookLiquidity newBook
  where (newBook, trades) = processSell book sell