A teacher is selecting a sample of 10 students from 80 by reading two-digit numbers from a random digit table. Each two-digit number has an 80% chance (i.e., probability $$0.80$$) of being valid. What is the expected number of two-digit pairs the teacher must read to obtain 10 valid, unique numbers?

Random Digit Table Sample:

| 12 | 85 | 47 | 33 |
| 76 | 09 | 81 | 50 |

Note: Sequences like 85 and 81 would be skipped since they exceed 80.