On December 1, Kate Holmes opened a speech and hearing clinic. During December, her firm had the following transactions involving revenue and expenses. Paid $2,400 for advertising. Provided services for $2,100 in cash. Paid $660 for telephone service. Paid salaries of $1,900 to employees. Provided services for $2,300 on credit. Paid $310 for office cleaning service. Did the firm earn a net income or incur a net loss for the period? What was the amount?