coefficient `cmult` (b0_term * b1_term * b2_term * b3_term)
where
denominator = (factorial i)*(factorial j)*(factorial k)*(factorial l)
- coefficient = 6 / (fromIntegral denominator)
+ coefficient = (6 / (fromIntegral denominator)) :: Double
b0_term = (b0 t) `fexp` i
b1_term = (b1 t) `fexp` j
b2_term = (b2 t) `fexp` k