The pair of quantities having same dimensions is

If an experiment four quantities a, b, c and d are measured with percentage error 1%, 2%, 3% and 4% respectively.

Quantity P is calculated as follows P $$ = {{{a^3}{b^2}} \over {cd}}$$ % error in P is

The dimensions of $${\left( {{\mu _0}{\varepsilon _0}} \right)^{ - 1/2}}$$ are

The damping force on an oscillator is directly proportional to the velocity. The units of the constant of proportionality are