Answer:
c. $990
Explanation:
I am assuming that the par value of the bonds is $1,000. If the market price of the bonds is above $1,000, IBM can choose to redeem them at par value. E.g. if market value is $1,049, they can redeem them at $1,000 resulting in a $49 gain.
But if the bonds are selling below par value (under $1,000), then IBM should redeem them at market price since they will spend less money. E.g. if the market price is $990, why would they buy them at $1,000?