Hello,

C is such that for any , (or here, it's for )

Since f and h are pdf, it follows that C>1.

Now, try to find a suitable C. It mustn't depend on x, but it can depend on mu and lambda.

For the method in general, it would be a start to read your lecture notes, or the wikipedia page ( Rejection sampling - Wikipedia, the free encyclopedia ), though the latter is not brilliant...