The figure at right is a pentagram inscribed in a circle.  A pentagram is a $5$-pointed star that has congruent angles at each of its outer vertices.  

1. Use the fact that all pentagrams can be inscribed in a circle to calculate the measure of angle $a$ at right.

   Answer (a):

   $36°$

2. What are the measures of angles $b, c,$ and $d$?  Show your work.

   Hint (b):

   $∠b$ is equivalent to $∠c$