Ten high energy cosmic rays hit detector in its first year, 7 in the second year, 11

Question:

Ten high energy cosmic rays hit detector in its first year, 7 in the second year, 11 in the third year, and 8 in the fourth and final year. Compare the likelihood with the maximum likelihood estimator of Λ with the likelihood if Λ = 10.0.
Find the likelihood as a function of the Poisson parameter Λ, find the maximum likelihood estimator, and evaluate the likelihood at the maximum and at the other given value of Λ.