DSE 2005 Question 9: Monopolistic competition and oligopoly

Consider a Cournot duopoly with inverse market demand $p=a-b(q_1+q_2)$, where $a>4$ and $b>0$ are constants, $p$ is the market price and $q_i$ is firm $i$'s output. Firm $1$'s cost function is $C_1(q_1)=q_1$ and Firm $2$'s cost function is $C_2(q_2)=2q_2$. In Cournot equilibrium, the outputs are