FRESNO, Calif. (KFSN) -- 20 people have been arrested and face charges for human trafficking and prostitution, according Merced Police.Officers conducted an undercover operation by responding to and posting online advertisements on known commercial sex websites.When contacted officers then negotiated sex acts for money and then arrested the suspect when they arrived to engage in acts of prostitution.In total, 20 people were taken into custody during the operation, including 10 men and eight women for solicitation of prostitution and two other men for pimping and supervision of prostitution.