a) To find the sum of the given arithmetic series, we can use the formula for the sum of an arithmetic series:

S = (n/2)(first term + last term)

In this case, the first term is 1 and the last term is 2023. The common difference is -1.

S = (2023/2)(1 + 2023)
S = (2023/2)(2024)
S = 1026126

Therefore, the sum of the series A is 1026126.

b) In this series, the first term is 1 and the last term is 313. The common difference is -3.

S = (313/2)(1 + 313)
S = (313/2)(314)
S = 49171

Therefore, the sum of the series B is 49171.

c) The sum of a single term is equal to the term itself. Therefore, the sum of the series C is -2194.21952195 + 2195.21942194 = 0.00009999.