campaign finance

Hadn't realized that there were meaningful challenges to campaign finance rules coming up. Thank goodness. I still don't understand: (i) why is a politician permitted to sell an advertisement (i.e., a book published in connection with a campaign) but not to buy an advertisement; (ii) how can it possibly be legal to penalize a candidate for private efforts on their behalf; and (iii) how can we possibly distinguish between spending money and giving time when it comes to campaign finance limits?