Water in a lake was polluted with sewage from a nearby town with 7mg of waste compounds per 1000l of water.

Water in a lake was polluted with sewage from a nearby town with 7mg of waste compounds per 1000l of water. It is determined that the pollution level would drop at the rate of 0.75 mg of waste compounds per 1000ℓ of water per year, if a plan proposed by environmentalists is followed. Let 2001 correspond to x = 0 and successive years correspond to x = 1, 2, 3,…. Find the equation y = mx + b that helps predict the pollution level in future years, if the plan is implemented