CAYLEY 2020 Problem 20

Past Contests CAYLEY CAYLEY - 2020
1

For how many pairs (m, n) with m and n integers satisfying 1 \leq m \leq 100 and 101 \leq n \leq 205 is 3^{m}+7^{n} divisible by 10?

Answer Choices
A. 2600
B. 2626
C. 2601
D. 2650
E. 2625