Matrices of stretching transformations of $\mathbb{R}^3$ and their eigenvectors

Consider the basis \(\vec { e } _ { i } , i = 1 , 2 , 3\) , in the vector space \(\mathbb { R } ^ { 3 }\) In this basis, write the matrix of the transformation that

1. stretches all directions by a factor of λ.

2. stretches each direction along \(\vec { e _ { i } }\) by a factor of \(\lambda _ { i } , i = 1 , 2 , 3\)

3. stretches the direction determined by a unit vector ~n with components \(n _ { x } , n _ { y } , n _ { z }\) by a factor of λ.

Find the eigenvectors of these transformations.