Write mechanisms for the reactions whereby HBr adds to 1-phenylpropene (a) in the presence of peroxides and

Question:

Write mechanisms for the reactions whereby HBr adds to 1-phenylpropene (a) in the presence of peroxides and (b) in the absence of peroxides. In each case account for the regiochemistry of the addition (i.e., explain why the major product is 2-bromo-1-phenylpropane when peroxides are present and why it is 1-bromo-1-phenylpropane when peroxides are absent).