Prove that the following grammar is ambiguous a b

Prove that the following grammar is ambiguous:

| <exp> * <exp>

| ( <exp> )

| a | b | c

exp => exp + exp

=>exp * exp + exp ( exp -> exp*exp)

=>a * exp + exp (exp ->a)

=>a*b+exp (exp->b)

=> a*b+c (exp->c)

exp =>exp + exp

=>exp+exp * exp (exp->exp * exp)

=>a +exp * exp (exp->a)

=>a+b*exp (exp->b)

=>a+b*c (exp->c)

thus this grammer defines two different derivations / parse trees.
So that it is said ambiguouse grammer.