A question in book 5 ,thanks. level 1

A straight 5% bond has two years remaining to maturity and is priced at $981.67.A callable bond that is the same in every respect as the straight bond ,expect for the call feature, is priced at $917.60. With the yield curve flat at 6%,what is the value of the embedded call option?

A $-82.40

B $45.80

C $64.07

D $101.00

This is my answer:

Consider the market yield has been up to 6%,the value of the call option should decrease . So B is the possible answer.

Why the answer in the book is C?

Thanks.