(1) When the suit is founded on an instrument of writing purporting to have been executed by the defendant, in which the demand of the plaintiff is liquidated, and if the signature of the defendant is not denied under oath, and if the instrument has been filed with the justice of the peace previous to the day for appearance, he may proceed with the cause, whether the plaintiff appears or not. The instrument of writing shall be competent proof in the case.
(2) In the case provided for in subsection (a) of this section, if the defendant does not appear in obedience to the summons, judgment shall be rendered against him for the amount of the plaintiff's claim.