A store sold 70 copies of a magazine for $350. Each copy of the magazine costs the same. Which equation and set of ordered pairs best represents the price (y), in dollars, of a certain number of copies (x) of the magazine?
A.y = 3x; (1, 3), (2, 6), (3, 9)
B.y = 4x; (1, 4), (2, 8), (3, 12)
C.y = 5x; (1, 5), (2, 10), (3, 15)
D.y = 6x; (1, 6), (2, 12), (3, 18)