Donna and Keith want to sell their business. They have received two offers. If they accept Offer A, they will receive $61,000 immediately and $20,000 in three years. If they accept Offer B, they will receive $37,000 now and $3,000 at the end of every six months for 5 years with the first payment received 6 months from now. If interest is 6.67% annually, which offer is preferable for Donna and Keith? Give proper explanation with formula, not answer solved with software.