Three identical isosceles triangle-shaped pieces in yellow, red, and blue colors are combined with their apex angles' vertices coinciding to form a fan. When the fan is opened, one side of each pair of adjacent pieces will be shared, and all pieces will be completely visible as shown in Figure 1.
When the fan is closed on a table, all pieces have one side on the table as shown in Figure 2.
According to this, what is the apex angle of the blue piece in degrees?
A) 18
B) 19
C) 20
D) 21
E) 22