A.) Geometric, sum of all terms is gotta be either -infinite, or all of that added up, I don't have the patience to work that out.
B.) No.
C.) 1+2+4+8+16+32+64+128+256=511, so n=9
D.) So uhh, I'm confused, but I think I get it. It's 4550, because 650+600+550+450...+150+100+50+0=4550
Someone smarter than me can do B.) because I'm lazy.
Yay!