10. Debt
On March 31, 2017, the Company entered into a
On March 31, 2017, the Company entered into a $400.0 million syndicated credit facility (“Credit Agreement”) that extends to March 2022. Interest on the borrowings under the Credit Agreement accrue at variable rates, based upon LIBOR or a defined “Base Rate,” both determined based upon the rating of the Company’s senior unsecured long-term debt (the “Debt Rating”). The applicable margin to be added to LIBOR ranges from 1.00% to 1.75% (1.25% as of June 30, 2019), and for Base Rate-determined loans, from 0.00% to 0.75% (0.25% as of June 30, 2019). The Company also pays a quarterly commitment fee ranging from 0.125% to 0.400% (0.20% as of June 30, 2019), determined based upon the Debt Rating, of the unused portion of the $400.0 million commitment under the Credit Agreement. In addition, the Company must pay certain letter of credit fees, ranging from 1.00% to 1.75% (1.25% as of June 30, 2019), with respect to letters of credit issued under the Credit Agreement. The Company has the right to voluntarily prepay and re-borrow loans and to terminate or reduce the commitments under the facility. As of June 30, 2019, the Company had $6.0 million of issued letters of credit under the Credit Agreement and $19.7 million of short-term borrowings, with the balance of $374.3 million available to the Company. As of June 30, 2019, the borrowing rate for the Credit Agreement was 3.90%.
The Company is subject to certain financial and restrictive covenants under the Credit Agreement, which, among other things, require the maintenance of a minimum interest coverage ratio of 3.50 to 1.00. The interest coverage ratio is defined in the Credit Agreement as, for any period, the ratio of consolidated earnings before interest, taxes, depreciation and amortization and non-cash net pension expense (“EBITDA”) to consolidated interest expense for such period. The Credit Agreement also requires the Company to maintain a debt to capital ratio of less than 55 percent. The debt to capital ratio is defined in the Credit Agreement as the ratio of consolidated indebtedness, as defined therein, to consolidated capitalization, as defined therein. As of June 30, 2019, the Company was in compliance with all of the covenants of the Credit Agreement.
Long-term debt outstanding as of June 30, 2019 and 2018 consisted of the following:
Aggregate maturities of long-term debt for the five years subsequent to June 30, 2019, are $0.0 million in fiscal years 2020, 2021, $250.0 million in 2022, $300.0 million in 2023 and $0.0 million in 2024.
For the years ended June 30, 2019, 2018 and 2017, interest costs totaled $31.1 million, $31.1 million and $31.1 million, respectively, of which $5.1 million, $2.8 million and $1.3 million, respectively, were capitalized as part of the cost of property, plant, equipment and software.
Table:
 | June 30, | 
($ in millions) | 2019 | 2018
Senior unsecured notes, 5.20% due July 2021 (face value of $250.0 million at June 30, 2019 and 2018) | $251.2 | $246.6
Senior unsecured notes, 4.45% due March 2023 (face value of $300.0 million at June 30, 2019 and 2018) | 299.4 | 299.1
Total | 550.6 | 545.7
Less: amounts due within one year | — | —
Long-term debt, net of current portion | $550.6 | $545.7


Question: What was the change in Total debt in 2019 from 2018?
Answer: 4.9
Calculation: 550.6-545.7