Quantity of bird nests in firm to be able to havest 1 kg per month

How many bird nests you need to have in your firm to be able to harvest 1kg of bird nest per month?
Assume:
1kg = 125 nest

Example: Your farm have 400 nests.  1 year you may able to harvest 1,200 nests (1 year 3 cycle, so 400 nest x 3). Harvest per month = 1,200/12 = 100 nests per month or 25% of 400 nests.
conclusion: you are able to harvest 25% of bird nests in the firm per month.

So, if you need to harvest 1kg = 125 nests per month, your firm need to have 500 nest (125nest/25%). Note25%=0.25

From the above, you can now easily estimate number of nest in a farm from the monthly harvest. Example: Firm A harvest 2.5kg per month.  You can easily say that Farm A have 1,250 nests in the firm
 (2.5 kg x 125)/25% = 1,250 nests.

Go and try whether my formula acceptable or not.