In 2018, Apple Inc. has massive liquid assets that generate a high interest rate of 8.58%. The cash, cash equivalents is $66,301 million, the short-term debt and current portion of long-term debt are $20,748 million, the long-term debt is $93,735 million. The average interest paid on debt is 2.83%. If we view the firm as proceeding to build up cash reserves while maintaining the amount of debt. What is the implied average cost of debt (assume the amount of net debt is unchanged from 2017 to 2018)?