Final answer:
Heather's basis in the common shares is $10 per share, and her basis in the preferred shares is $100 per share.
Step-by-step explanation:
Heather's basis in the common shares is determined by the amount she paid for the shares. She paid $4,000 for 400 shares, so her basis in the common shares is $10 per share ($4,000 รท 400 shares).
For the preferred shares received as a nontaxable stock dividend, Heather's basis is equal to the fair market value of the shares on the date of distribution. Since the fair market value of the preferred shares is $100 per share, her basis in the preferred shares is $100 per share.
To summarize, Heather's basis in the common shares is $10 per share, and her basis in the preferred shares is $100 per share.