At a certain gas station, 70% of the customers use regular-grade unleaded gas and 30% use higher-grade unleaded gas. It is also known that among the customers using regular-grade gas, 60% will fill their tanks; among the customers using higher-grade gas, 80% will fill their tanks.
1. What is the probability that the next customer will request higher-grade unleaded gas and fill the tank?
2. Assume the probability that a customer fills the tank is 0.66. If the next customer fills the tank, what is the probability that higher-grade gas is required?