Need to create step wise ramp up scenario

Hi,

Need to create scenario with 20 users rampup - 2 users every 5 secs , steady state for 20 mins. After which 30users to be ramped up- 5 users every 5secs , later steady state for 30mins. Finally all 50 users ramp down - 2 users every 5 secs

Thanks,
Santhosh