12. (5%) Let For what value(s) ofh is b in the plane spanned by al and a2? (A) 0 (B) -10 (C) 16 (D) -17 (E) 20

4. (5%) Consider the equationwiththe boundary conditions y(0)=0.y(π)=π.Which statements are correct? (A) The particular solution is yP =-x. (B) The general solution is y=ex sinx+x. (C) There is a unique solution to this boundary-value problem. (D) This differential equation is homogencous. (E) None of the above.