The rate constant of a first order reaction depends on

For the decomposition of ${\mathrm{N}}_2{\mathrm{O}}_5( \mathrm{g})$ it is given that- 

$2 {\mathrm{N}}_2{\mathrm{O}}_5( \mathrm{g})\to 4{\mathrm{NO}}_2( \mathrm{g})+{\mathrm{O}}_2( \mathrm{g})$ 

activation energy $=\mathrm{Ea}$

${\mathrm{N}}_2{\mathrm{O}}_5( \mathrm{g})\to 2{\mathrm{NO}}_2( \mathrm{g})+\frac{1}{2}{\mathrm{O}}_2( \mathrm{g})$

activation energy $= \mathrm{Ea}\text{'}$ then

The rate of reaction increases by the increase of temperature because: