An outstanding issue of Jeronimo Martins bonds has a call provision attached. The total principal value of the bonds is €120 million, and the bonds have an annual coupon rate of 6.6 per cent. The total cost of refunding would be 12 per cent of the principal amount raised. The appropriate tax rate for the company is 12.5 per cent. How low does the borrowing cost need to drop to justify refunding with a new bond issue?