Determine all eigenvalues and eigenvectors of the matrix a = [2 1 2 3]. (the eigenvector/eigenvalue problem comes up in the study of homogeneous systems of differential equations, chapter 8)

Mrs. morton has a special reward system for her class. when all her students behave well, she rewards them by putting 3 marbles into a marble jar. when the jar has 100 or more marbles, the students have a party. right now, the the jar has 24 marbles. how could mrs. morton reward the class in order for the students to have a party?