In the analytic plane, the sides of a regular pentagon are named as vectors $\vec { a } , \vec { b } , \vec { c } , \vec { d }$ and $\vec { e }$ as shown in the figure.
Accordingly, what is the probability that the dot product of two vectors randomly selected from these five vectors is positive?
A) $\frac { 1 } { 2 }$
B) $\frac { 1 } { 5 }$
C) $\frac { 2 } { 5 }$
D) $\frac { 1 } { 10 }$
E) $\frac { 3 } { 10 }$