I have this exercice and i want to know how to solve it :
1)- Let $X,Y$ two separable metric spaces ,let $(\Omega, \mathcal{A})$ be a measurable space ,and $f: \Omega \rightarrow X$ a measurable function and $\varphi :\Omega \times X \rightarrow Y$ a Cartheodory function ,then the map: $\Omega\rightarrow Y$, $x\mapsto \varphi (x,f(x))$ is measurable .
please; i don't know how to start .