Was this done correctly?

Was this done correctly?
You have to be at a job interview that is 600 miles away and it starts in 10 hours.
You’re average speed over the first 5 hours is 40 mph. What does your average speed
need to be in the remaining 5 hours of the trip to make it on time? Do you think you
can make it without speeding if the speed limit is 60mph?
I need to go 600 miles in 10 hours so my average speed needs to be 60 mph. This is the
same as finding the slope between the endpoints (0, 0) and (10, 600) which is
600 − 0
= 60 mph.
10 − 0
So yes I can make it without speeding!