Capacity expansion and entry deterrence

I'm using the Dixit model...

The inverse market demand function is:

$p=100- \frac{q}{2}$

$w=10 \,$

$r=30$

To start I have to find firm 2's (the entrant) best response function after it has decided to enter.

I have:

$q_2=\frac{100-\frac{q_1}{2}-(w+r)}{2}$

$=\frac{200-80-q_1}{4}$

$=\frac{120-q_1}{4}$

Look good?