Time taken for $12.8\mathrm{g}$ of a radioactive substance to decay to $0.4\mathrm{g},$ is (half-life is $138\mathrm{s}$)

In the following reaction, how is the rate of appearance of the underlined product related to the rate of disappearance of the underlined reactant ? 

${\mathrm{BrO}}_{3\left(\mathrm{aq}\right)}^{-}+\underline{5{{\mathrm{Br}}^{-}}_{\left(\mathrm{aq}\right)}}+6{\mathrm{H}}_{\left(\mathrm{aq}\right)}^{+}⟶3\underline{{\mathrm{Br}}_{2\left(\mathrm{l}\right)}}+3{\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{l}\right)}$

$3\mathrm{A}⟶2\mathrm{B},$ rate of reaction $+\frac{\mathrm{d}\left[\mathrm{B}\right]}{\mathrm{dt}}$ is equal to

The temperature dependence of rate constant $\left(\mathrm{k}\right)$ of a chemical reaction is written in terms of the Arrhenius equation, $\mathrm{k}={\mathrm{Ae}}^{-{\mathrm{E}}_{\mathrm{a}}/\mathrm{RT}}$. The activation energy $\left({\mathrm{E}}_{\mathrm{a}}\right)$ of the reaction can be calculated by plotting