The separation of two coloured substances was done by paper chromatography. The distances travelled by solvent front, substance A and substance B from the base line are 3.25 cm, 2.08 cm and 1.05 cm, respectively. The ratio of R_f values of A to B is _____________.

The total number of monobromo derivatives formed by the alkanes with molecular formula C₅H₁₂ is (excluding stereo isomers) __________.

Observe structures of the following compounds

The total number of structures/compounds which possess asymmetric carbon atoms is ______________.

Total number of possible stereoisomers of dimethyl cyclopentane is ____________.