CAYLEY 2021 Problem 21

The variables a, b, c, d, e, and f represent the numbers 4,12,15,27,31, and 39 in some order. Suppose that

\begin{aligned} & a+b=c \\ & b+c=d \\ & c+e=f \end{aligned}

The value of a+c+f is

Answer Choices
A. 58
B. 70
C. 73
D. 82
E. 85