Use the approach in Gauss's Problem to find the following sums of arithmetic sequences.

a. 1+2+3+4+...+998
b. 1+3+5+7+...+97
c. 2+5+8+11+...+302
d. 908+899+890+881 +...+8

The sum of the sequence is.. ??

Please help I’ll mark you as brainliest if correct!