[Haskell-cafe] multMM :: Matrix -> Matrix -> Matrix --multiplies two matrices question (Homework)

hi i was trying to solve it but All i got is type Matrix=[[Double]] multMM :: Matrix -> Matrix -> Matrix --multiplies two matrices multMM m t = [[sum (zipWith (*) (head m)(a)) ] ]where a = [head a | a<- t] Main> multMM [[2,1,-6],[1,-3,2]] [[1,0,-3],[0,4,20],[-2,1,1]] [[14.0]] from this i could get only the first multiplication 14 that is by 2*1 + 1*0 + -6*-2 = 14 how can i make this go throw all rows and colums to get multiple of matrixs? Thank you~