Hello everybody. Need some help on this:

Let $\displaystyle X-\varepsilon(\lambda)$

and

$\displaystyle P(x)-p(x)=1-(e^{-ax}+ae^{-\lambda x})$

where $\displaystyle P(x)$-distribution function and $\displaystyle p(x)$-density for $\displaystyle X$

Determine $\displaystyle a$!