A callable par-value bond has the coupon rate r and F = C, with n semiannual coupon. The call date is at the moment of k-th coupon. For all m = k, k + 1, . . . , n, let Pm denote the price to yield interest i assuming that the bond is called immediately after the m-th coupon has been paid. If r < i, show that Pm forms a decreasing sequence.