Adjusting Entries: Stephen King, D.D.S. opened a dental practice on January 1, 2010. During the first month of operations the following transactions occurred: Performed services for patients who had dental plan insurance. At January 31, $1,000 of such services was earned but not yet billed to the insurance companies. Salaries were incurred totaling $650 but not paid at month-end. Supplies totaling $600 were purchased on account. Prepare the adjusting entries on January 31.