Haskell Question

I have the following code:

-- Represent a 2x2 matrix, e.g.,

-- ( 3 1 )

-- ( 4 0 )

-- becomes

-- MkMat 3 1 4 0

data Mat a = MkMat a a a a

deriving (Eq, Show)

How can I write the following functions for addition, negation and multiplication?

instance Num a => Num (Mat a) where

(+) :: Mat a -> Mat a -> Mat a

negate :: Mat a -> Mat a

(*) :: Mat a -> Mat a -> Mat a