Sorry to botter you again but this I can't solve. I really need your help

I posted it before but the format of the matrix was crappy

Let A = (1 -2

-1 2

0 3

2 5)

and b = ( 3

1

-4

2)

(a) Find a least-squares solution ofAx = b.

(b) Find the orthogonal projection ofbonto the column space ofA.

(c) Compute the least-squares error ( in the solution of part ( a )).

Thank you!