Find the Measure of the Dihedral Angle Indicated $40 ^ { \circ }$

Multiple Choice

Find the measure of the dihedral angle indicated.
-The figure shown is a right prism whose bases are regular nonagons. Find the measure of the dihedral angle between adjacent lateral faces.

A) $40 ^ { \circ }$
B) $144 ^ { \circ }$
C) $90 ^ { \circ }$
D) $140 ^ { \circ }$