Given the environment: \mu l(a,b:N):N:={(0,:b=0),(a,:b=a),(a+\mu\nl(a,b-1),: otherwise ):} Prove: AAa,b:N*\mu l(a,b)=a*b

What is the purpose of the environment \mu l(a,b:N):N:={(0,:b=0),(a,:b=a),(a+\mu\nl(a,b-1),: otherwise ):} and what does it represent?

A) A function that calculates the product of two numbers
B) A function that calculates the sum of two numbers
C) A function that calculates the difference of two numbers
D) A function that calculates the quotient of two numbers