Two firms compete in quantities (Cournot competition). The inverse demand function is $P = 150 - Q_1 - Q_2$, where $Q_1, Q_2$ are the quantities produced. Firm 1 has a constant marginal cost $c_1 = 30$ and Firm 2 has a constant marginal cost $c_2 = 45$. What are the Nash equilibrium quantities $(Q_1^*, Q_2^*)$?