A bean plant grows at a constant rate for a month. after 10 days, the plant is 30 centimeters tall. after 20 days, the plant is 50 centimeters tall. which equation models the height of the plant, y, after xdays?
a.y-30=(x-10)
b.y 30=(x 10)
c.y-30=2(x-10)
d.y-10=2(x-30)