Ecto parasite poultry are controlled by

“Ectoparasites,” or parasites that feed on the outside of the body, may cause considerable loss to a poultry operation, particularly by lowered egg production. ... Infestations of external parasites on poultry can be economically controlled with good sanitation and with proper use of insecticides.

a=c and then d= c because of the band so you get ac/dc and you add them together you get sound waves