On December 1, Karl Zant opened a speech and hearing clinic. During December, his firm had the following transactions involving revenue and expenses.

Paid $2,100 for advertising.

Provided services for $1,800 in cash.

Paid $600 for telephone service.

Paid salaries of $1,600 to employees.

Provided services for $2,000 on credit.

Paid $250 for office cleaning service.

Did the firm earn a net income or incur a net loss for the period? What was the amount?