The bar graph to the right shows estimates of the top six national debts (in trillions of dollars). Use the bar graph to estimate the national debt of Country B and then express it in both standard and scientific notation. National Debt (in trillions of dollars) 18- 16- 14- 12- 10- 8- 6- Top Six National Debts A B D Express the national debt of Country B in standard form. OA. 4,000,000,000,000 OC. 4,000,000,000 OB. 15,800,000,000, OD. 15,800,000,000