A hypothetical question

McMamouth Corporation is a Delaware corporation with its principal place of business in California.Although it has no regular place of business in Texas, McMamouth.It also transacts a substantial amount of intrastate business within Texas, and has registered to do business in Texas and appointed Ronald Donald as its registered agent for service of process as required by the Business Organizations Code.Polly Petal contracted with McMamouth to provide live floral arrangements to all of its Dallas area stores. Polly did so, but McMamouth refuses to pay. Polly wants to sue McMamouth for breach of contract. How should she serve it with process under Texas law?