i get around 5400 EM per hour with 278k MPH.
So to get 350k EM every 3 days, or 117k EM a day, you only need to earn 4875 EM per hour. So you can do that with 250k MPH.
Sidenote:
Detegrets, how can you know that you earn 2k EM an hour with 100k Mining and think you need 700k mph to earn 350k EM every 3 days?