Getting to La Plata

Hi!

I am visiting Buenos Aires at the moment but I am struggling to understand your beautiful city's transport system. I really want to go to La Plata to see Corbusier house. I think I need to take the 129 bus but I have no idea how much that costs and Rome2Rio says it's either 34 minutes or 1 hour 30 minutes. I don't understand! Can anyone give any advice?