Zoho Invoice: 2 rates ( B2B rate and B2C rate)

Zoho Invoice: 2 rates ( B2B rate and B2C rate)

Hi,
 
I would need to set up a B2B rate and a B2C rate for my items.
Could you please provide a solution ?
 
NB:
 
- When some clients order for 50 units of the same item I'd like to apply a B2B rate (8 €/ units)
- When other client order only 2 unites of the same item I'd to apply a B2C rate (15€/units)
 
Regard,