Each of the variables a, b, c, d, and e represents a positive integer with the properties that
\begin{aligned}
& b+d>a+d \\
& c+e>b+e \\
& b+d=c \\
& a+c=b+e
\end{aligned}
Which of the variables has the greatest value?
Answer Choices
A. a
B. b
C. c
D. d
E. e