TRAIN FROM BUCHAREST TO VARNA???!!!!!!?

How much is a train or bus ride ride from Bucharest, Romania to Varna, Bulgaria? Is it non-stop, how much Euro and how many hours is it for both? Better yet which one is best to take? I know Varna is a summer city but is it still ok to visit Varna in the beginning of October? Will it still be a little warm during the day? Someone who is from there please answer thanks