Not for points English to Spanish Bus/Financial Accounting

Buenas tardes:

El problema es que no sabría cómo traducir este verbo en este contexto.

Tengo varios términos posibles, peor no estoy segura:
- Requerir fondos
- Retirar de circulación
- Opción de compra


Contexto:

If a company has outstanding bonds with a sinking fund provision and if interest rates have (List A) since the bonds were issued, then the company would realize a savings in meeting its sinking fund obligations by (List B).

List A List B
a.Increased Buying back bonds in the open market
b.Remained constant Calling in a portion of the bonds at face value
c.Increased Calling in a portion of the bonds at face value
d.Decreased Buying back bonds in the open market

Answers
A: A.
B: B.
C: C.
D: D.
Answer Explanations
Answer (a) is the correct answer. If interest rates have increased, then the bonds will be selling at a discount, below face value, in the open market. It will be cheaper for the company to retire a portion of the outstanding bonds by buying them back in the open market at the discounted price, rather than calling in a portion of the bonds at face value.
Answer (b) is incorrect because if interest rates have remained constant, the bonds will still be selling at face value in the open market. The cost of buying bonds back on the open market will be the same as the cost of calling in a portion of the bonds at face value.
Answer (c) is incorrect because if interest rates have increased, then the bonds will be selling at a discount in the open market. Buying back bonds in the open market will therefore be the cheaper alternative, not calling in a portion of the bonds at face value.
Answer (d) is incorrect because if interest rates have decreased, then the bonds will be selling at a premium in the open market. It will be more costly, not less costly, to retire a portion of the outstanding bond issue by purchasing bonds on the open market. It will be cheaper to meet the sinking fund obligations by calling in a portion of the bonds at face value.

Muchas gracias por su ayuda!!!!