E3-6 (Adjusting Entries) Stephen King, D.D.S., opened a dental practice on January 1, 2015. During the fifst month of operations, the following transactions occurred. 1. Performed services for patients who had dental plan insurance. At January 31,$750 of such services was performed but not yet billed to the insurance companies. 2. Utility expenses incurred but not paid prior to January 31 totaled $520. 3. Purchased dental equipment on January 1 for $80,000, paying $20,000 in cash and signing a $60,000, 3-year note payable. The equipment depreciates $400 per month. Interest is $500 per month. 4. Purchased a one-year malpractice insurance policy on January 1 for $15,000. 5. Purchased $1,600 of dental supplies. On January 31 , determined that $400 of supplies were on hand