please help me answer this game theory question

Consider the game with this strategic form. Notice that it a is a symmetric game. (a) Write all pure-strategy Nash equilibria. (b) Let p,q, and r be Player I's, Player 2's, and Player 3's probability of choosing A, respectively, so that their mixed strategies are (p,1p),(q,1q), and (r,1r). What condition must q and r satisfy in order for Player 1's only best-response to be (1,0) ? (c) List the equations (in p, q, and r) that must hold in order for {(p,1p),(q,1q), and (r,1r)} to be a mixed-strategy Nash equilibrium? (d) Find two symmetric mixed-strategy Nash equilibria for this game