The first case: if they are all within 10 degree, then B is at most 10 degree, and * * spent 4.50 yuan, then C only spent 4.50-3.75 = 0.75 yuan, which is not an integer degree, and does not meet the meaning of the question.

In the second case, C is within 10 degree, and B is above 10 degree. Then the excess is 0.80 yuan per extra degree, and 3.75 yuan can be: 0.45+3.30, 0.45× 3+2.40, 0.45× 5+ 1.50, 0.45× 7+0.60, that is, 0.45× 3+2.40.

Looking at the relationship between A and B, A is 7. 10 yuan more than B, within 20 degrees, 20- 13 = 7 degrees, and the extra money is 7 × 0.80 = 5.60 yuan, 7.10-5.60 =1. Therefore, we can get that a is 20+ 1 = 2 1 degree.

Therefore, the electricity fee paid by Party A is:10× 0.45+10× 0.80+/kloc-0 /×1.50 =14.00 (Yuan).

Party B's electricity fee is: 10× 0.45+3× 0.80 = 6.90 (Yuan).

The electricity fee paid by Party C is 7× 0.45 = 3. 15 (RMB).