C-13-Q118mediumsingle_mcqThe sum of the first 888 terms of 1+12+14+18+⋯1 + \dfrac{1}{2} + \dfrac{1}{4} + \dfrac{1}{8} + \cdots1+21+41+81+⋯ is —a255128\dfrac{255}{128}128255b12764\dfrac{127}{64}ব্যাখ্যাWith a=1a=1a=1, r=12r=\tfrac12r=21, n=: .