i need complete soultion of this problem

Monitored natural attenuation is considered as a treatment alternative for the remediation of a groundwater plume contaminated with an organic contaminant. The natural attenuation rate of this contaminant is 0.0076 day 1. The contaminant concentration at the source is 13mg/L and the nearest receptor is 400m away from the source. The groundwater flow velocity, and the velocity of the contaminant in the groundwater, is 0.3m/ day. Is MNA a viable treatment alternative for this site if the maximum contaminant concentration at the nearest receptor is 0.005mg/L ? What is the closest possible distance from the source to a receptor for MNA to still be effective