How do you find the least common multiple of these two expressions 9y⁴u⁷ and 15y³u⁵v⁶?
a) 135y⁴u⁷v⁶
b) 45y⁴u⁷v⁶
c) 135y³u⁵v⁶
d) 45y³u⁵v⁶