How Do We Calculate the Mass of Binary Stars Like Centauri A and B?

[PSEYE]

Homework Statement

Centauri A and Centauri B are binary stars with a separation of 3.45x10^12m
and a period of 2.52x10^9s

Assuming the two stars are equally massive (which is approximately the case), determine their mass.

Homework Equations

( m1 + m2 ) P^2 = ( d1 + d2 )^3 = R^3
I used this and it doesn't work :x

The Attempt at a Solution

M1=M2
D1=D2

M(2.52x10^18)=3.45x10^36

M=3.45x10^36/2.52x10^18

= wrong :X

 

[loonychune]

$${(2.52 \times 10^9)}^2 \neq 2.52 \times 10^{18}$$