But in this case by doubling A we essentially double v if everything else is kept constant. But if we double A and B and we keep K constant then we quadruple the value of v and finally we can also have 0th order. And in the 0th order basically the concentration of the reactant has no effect on the rate of that reaction. So if a reaction is 0th order with respect to some reactant then the rate is independent of that reactant's concentration. For instance, if we have A and A is transformed into B and K is the rate constant and we know that A is zero's order, what that basically means is the exponent will be zero. This will become one.