Exercise 4.3.8

$\hat{x}=a^{T}b∕a^{T}a=56∕13$ and $p=(56∕13)(0,1,3,4).(C,D)=(9,56∕13)$ don’t match $(C,D)=(1,4)$ from Problems 1-4. Columns of $A$ were not perpendicular so we can’t project separately to find $C$ and $D$.