Finding lambda for Poisson distribution with artifact density

[magma_saber]

Homework Statement

In one of the archaeological excavation sites, the artifact density (number of prehistoric artifacts per 10 liters of sediment) was 1.0. Suppose you are going to dig up and examine 50 liters of sediment at this site. Let r = 0, 1, 2, 3,… be a random variable that represents the number of prehistoric artifacts found in your 50 liters of sediment. Find the probability that you will find 1 or more artifacts in the 50 liters of sediment. Round your answer to the nearest ten thousandth.

Homework Equations

P(r) = (e^-lambda)*(lambda^r)/r!

The Attempt at a Solution

What is lambda? is it 10? or is it 10/50=0.2? i can't seem to figure it out.
i think r = 1

 

[vela]

λ is the number of artifacts in the 50 liters of sediment on average.

P(1) would be the probability you'd find exactly one artifact in the 50-liter sample, but the problem is asking you to find the probability of finding one or more. So you can't just set r=1 to get the answer you're looking for.