A Mechanism That Explains the Rate Law,Rate = K[(CH₃)₃CO₂C(CH₃)₃],for the Gas-Phase

A mechanism that explains the rate law,Rate = k[(CH₃) ₃CO₂C(CH₃) ₃],for the gas-phase thermal decomposition of di-tert-butyl peroxide is given below. For this proposed mechanism,the rate-determining step(s) must be

A) step 1.
B) step 3.
C) step 2.
D) step 1 + step 2 + step 3.
E) 2 times step 2.