A floor is tiled with a pattern consisting of regular octagons and squares as shown. Find the measure of each angle at the circled vertex. Then find the sum of the angles.
a. 135°, 90°, 1350, 360°
b. 90°, 90°, 90°. 270°
c. 135º. 135, 1359, 4050
d. 1200,120, 120°, 360°