Mode of action of aldehydes and Quaternary ammonium compounds is

Aldehydes have antibacterial, antifungal, antiviral and sporicidal activity. These are helpful to destroy the spores of Bacillus subtilis and Clostridium sporogenes. Glutaraldehyde and formaldehyde are commonly used aldehydes in disinfectants.

Quaternary ammonium compounds work by denaturing the proteins of the bacterial or fungal cell, affecting the metabolic reactions of the cell and causing vital substances to leak out of the cell, causing death.

to figure the total magnification of an image that you are viewing through the microscope is really quite simple. to get the total magnification take the power of the objective (4x, 10x, 40x) and multiply by the power of the eyepiece, (usually 10x)