Please help with this practice question.

There are 2 firms that sell a certain software, Microsoft and Oracle. Microsoft invented the software and so they act as a market leader by first deciding how much ofthe software they are going to produce each month. Oracle observes this decision by Microsoft and then chooses how much they are going to produce. The marginal cost of producing the software is constant at $2 for both companies. The total market demand for the software is P = 84 - 0.2Q. According to the Stackelberg model, what price will both companies sell the software at? [Write answer without the dollar Sign.)