Projection, Linear transformation, maybe change of basis.

This is my problem.

Let V=Span([1,0,2,1],[0,1,-1,1]) . Find the standard matrix for the linear transformation .

Here is my thinking.

Setting the matrix . This would be the transformation matrix with respect to the given basis of V. Normally, the standard matrix T would be but A cannot be because that is not a square matrix and obviously not invertible. What do I do?

Maximum explanation please because I am still trying to wrap my head around these concepts. Thanks!!!