Calculating power of one of two resistors

[carpelumen]

Homework Statement

Two resistors R1 and R2 are connected in series to a battery supplying a voltage of ∆V as shown. How much power is dissipated by the resistor R2 in the form of heat? Use the following data: R1 = 10 Ω, R2 = 5 Ω, ∆V = 3 V
http://tinypic.com/r/153tr91/8

2. Homework Equations
Rtotal = R1 + R2
P=V^2/R
P= I^2 x R

The Attempt at a Solution

Rtot = 10 + 15 = 15 ohms
I = 3/15 = .2 A
P = (.2^2) x 10 = .4 WWhy is this the wrong answer??

 

[whdahl]

Because R2 = 5 Ohms, not 10 Ohms