Contractual Terms and Hearsay

Action for the purchase price of a television set bought by D from the Acme TV Company. P's complaint alleges the following:

(1) Acme sold and delivered a television to D on June 1 on credit;

(2) D has failed to pay for the television in breach of the credit agreement;

(3) Acme assigned its claim to P on September 1;

(4) On September 15 P demanded payment from D; D refused; and

(5) P's claim is now due and unpaid, whereby P demands judgment for the purchase price.

D's answer alleges that P is not the real party in interest. At trial, P testifies that on September 1 he proposed to Acme that Acme assign its claim to him and that Acme then executed a document marked Plaintiff's Exhibit 1 for identification. Exhibit 1 states: "Acme TV Company hereby assigns its claim against D to P for good and valuable consideration." D objects and moves to strike P's testimony and to exclude Exhibit 1. What ruling and why?