12. Valeriu draws a zig-zag line inside a rectangle, creating angles of $10^{\circ}, 14^{\circ}, 33^{\circ}$ and $26^{\circ}$ as shown. What is the size of the angle marked $\theta$ ?
A $11^{\circ}$
B $12^{\circ}$
C $16^{\circ}$
D $17^{\circ}$
E $33^{\circ}$
12. A Add to the diagram three lines parallel to two of the sides of the rectangle, creating angles $a, b, c$, $d, e$ and $f$ as shown.
Since alternate angles formed by parallel lines are equal, we have $a=26^{\circ}$ and $f=10^{\circ}$. Since $a+b=33^{\circ}$ and $e+f=14^{\circ}$, we have $b=7^{\circ}$ and $e=4^{\circ}$. Similarly, since alternate angles are equal, we have $c=b=7^{\circ}$ and $d=e=4^{\circ}$. Therefore $\theta=c+d=7^{\circ}+4^{\circ}=11^{\circ}$.