A store sold 50 copies of a magazine for $150. Each copy of the magazine costs the same. Which equation and set of ordered pairs best represents the price, in dollars, of a certain number of copies 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)