When to find C

[Rup]

Hello,
How would I know that first I need to find C in such kind of problems?

An insurance company’s monthly claims are modeled by a continuous positive random variable X whose probability density function is proportional to (1+x)^-4 , where 0<x<infinity . Determine company’s monthly claims. (1/2)

Thanks

Rup

[Ken]

Since it specifies that the density function is proportional to f(x), you know you need to find C.