I need help with part d only

Styrene is polymerized using benzoyl peroxide as the initiator (free-radical chain-growth process) in solution. The initial monomer and initiator concentration are 1 molar and 0.001 molar, respectively. Determine the following (a) rate of initiation at 1min and 1000min. (b) steady-state free-radical concentration at 1min. (c) rate of polymerization at 1min. (d) halflife of the initiator at this polymerization temperature. The rate constants and initiator efficiency at this polymerization temperature are as: kd=2105s1;kp=200(molars)1;kt =8107(molars)1;f=0.7