This is my personal opinion. I am not a professional domainer. If someone thinks I have valued these domains too highly or to low, feel free to tell me.
Secretarial.services: $500 USD. New gTLDs do carry a risk which companies may not be keen to take, thus reducing potential value, especially considering the length of your chosen TLD. However, this domain name is pronounceable.
Secretarial.biz: $750 USD. The TLD .biz doesn't carry as much of the "new gTLD" stigma as .services, and is somewhat shorter than secretarial.services, but it still isn't that popular/desirable of a TLD (at least, I don't think it is. Please correct me if I am wrong).
Sincerely,
Cybercell