Particles are suspended in a liquid medium at a concentration of 4 particles per mL. A large amount of the suspension is thoroughly agitated, and then 3 mL are withdrawn . Let $X$ be the number of the particles in the 3 mL. Answer the following:
a- The distribution of X is a Poisson distribution, what is its parameter ($\lambda$)?
b- Find the probability that no particle is withdrawn from the 3 mL.
c- Find the probability that one particle is withdrawn from the 3 mL.