What is a reasonable fee to pay to zap someone some sats?

For example, your balance is 100 sats and you want to zap someone 21 sats.

a) 1 sat fee is ok, balance is now 78 sats

b) up to 10 sat fee, but you are charged 3 sats by your custodial provider leaving you a balance of 76 sats

c) up to 200 sat fee, but you are charged 3 sats leaving you a balance

d) always only zero. if a provider wants to charge a fee you dont send sats and your balance remains 100

Please comment

#pollstr