20. A gardening store is keeping track of the growth height of different plant types over a month. The table shows the growth height in centimeters for the first, second, third, and fourth weeks.
Week 1 - 12 cm
Week 2 - 18 cm
Week 3 - 24 cm
Week 4 - 30 cm
Which equation represents the relationship between the week number n and the growth height h in centimeters?
a) h = 6n + 6
b) h = 6n - 6
c) h = 6n^2
d) h = 6n/2