He earns 1020$
he is going to work 70 hours so :-
First 40 hours are each for 12$ so they will cost 480$ as a total
Then the next 10 hours will cost 6$ so 60$ as a total
since he is going to work for 70 hours then there are more 20 hours which will be charged for double(24$) each so 480$ as a total
So he earned 480$+60$+480$=1020$ in 70 hours
