Katy was tidying up around her apartment when she found bed bugs! She called her friend, Ms. Grant, who told her that she could spray an insecticide or put out sticky traps. Determined to decide which treatment is best, Katy tried both at the same time. She counted the bugs and then sprayed and laid out sticky traps. After one week, she counted the number of bugs she saw.

What are the constants of the experiment?​