Check the answer

May 17, 2020   photos  

For those who say 600 amp, you are right if we were talking about current, but that is not the case here. The unit for that 600s in each battery is clearly written as Ah (ampere×hour) so obviously it is the capacity of each battery and it varies with the number of cells in the circuit. The correct answer would be 24 V and 1200 Ah.
Finally, The two batteries in parallel V=12v again these batteries in series V=12+12=24v then current I= 300+300=600A