Irina has 10 coins, all nickels and dimes, worth a total of $0.70. This is shown by the system of linear equations, x + y = 10 and 0.05x + 0.1y = 0.7, on the graph. A coordinate grid showing Irina's Change with Number of Nickels on the x-axis and Number of Dimes on the y-axis with 2 lines. The first line passes through (0. 10) and (8, 4). The second line passes through (0, 7) and (8, 4).
How many nickels does she have?

4
6
7
10