How much memory we need for DriverLocationHT?

[Dewey_Munoz]

How much memory we need for DriverLocationHT? We need to store DriveID, their present and old location, in the hash table. So, we need a total of 35 bytes to store one record:

1. DriverID (3 bytes - 1 million drivers)
2. Old latitude (8 bytes)
3. Old longitude (8 bytes)
4. New latitude (8 bytes)
5. New longitude (8 bytes) Total = 35 bytes

why do we need the old lat/long in the uber driver location hash table?