Suppose in a soft drink market, the demand curve is linear and is given as follows: P = 30 - Q The marginal cost to produce this new drink is constant at $3. Determine the equilibrium price in the following scenario respectively:

(a) The market is a perfectly competitive market;

(b) The market is a monopoly market;

(c) The market is a Cournot market (where there are only two firms and they act simultaneously);

(d) The market is a Stackelberg market (where there are only two firms and one of the firms has a first mover advantage).