The difference between the average of first ten prime numbers and the first ten prime numbers of two digit is:

First 10 primes: 2,3,5,7,11,13,17,19,23,29 — average = 129/10 = 12.9. First 10 two-digit primes: 11,13,17,19,23,29,31,37,41,43 — average = 264/10 = 26.4. Difference ≈ 13.5. The correct answer per key is 12.5.