Coefs

Key Coefs in Product Fn refers to the coefficients (weights) m₁, m₂, ..., mᵣ that multiply the corresponding input variables as described in Product Fn
It must be an array of numbers with r elements, whereby r can be any non-negative integer.
An empty array is admisible and results in a function that returns a constant.
The size r of this array defines the number of input parameters that contribute to the function output.
Generally it also equals the minimum expected number of input parameters, although the latter may be greater if a special array is entered in Input Variables