proof that a recursion is true using induction

Proofs of Correctness 1-7. [3 Prove the correctness of the following recursive algorithm to multiply two natural numbers, for all integer constants c2 2. function multiply(y, z) comment Return the product yz. 1.if z -0 then return(0) else 2. 2. return multiply(cy, Lz/c]) +y (z mod c))