How much does this cost to the nearest dollar?

Carbon Monoxide Detectors, 2pcs CO Alarm Detector, Carbon Monoxide Alarm with LCD Digital Display (Batteries NOT Included)
High Sensitive Using electrochemical sensors, with more reliability, stability, responsiveness, to avoid the possibility of false readings and false alarms. Light and Sound Alarm Warning When a dangerous level of carbon monoxide is detected the red LED will flash and the alarm pattern will sound alarm to protect your family's life and property safety. LCD Displayer Carbon monoxide alarm detector With 3 digits LCD displayer is optional,'Err' on the LCD to indicate the unit is malfunctioning. 'Lb' on the LCD to indicate is low battery and need to replacement. on the LCD is normal phenomenon. Alarm Standard 50ppm - Alarm within 60 to 

Price is $23.00

Price: $22.9