User turns:
user: In attempting to log into my travel account using both my established client id 'client_520', secret 'rise_to_sky' and refresh token 'token990125', I seem to be at a bit of an impasse, allow for read_write. 
user: Right, my first name is Michael, last name Thompson. Assistance with the authentication process would be immensely appreciated.
user: I've recently linked a newly registered credit card with the ID 'card_4455', set to expire in 2024, and it's under my name. Accessing my account to ascertain my current balance is my next goal. Could this information be retrieved for me?
user: Having reviewed my financial standing, I now need to compute the average amount spent in my last quintet of purchases, which are 45.99, 78.25, 102.50, 38.75, and 92.10. Guidance in deriving this mean value would be beneficial.

Involved APIs: MathAPI
TravelAPI
Ground-truth function call path:
TravelAPI.authenticate
TravelAPI.register_credit_card
TravelAPI.get_credit_card_balance
MathAPI.mean