I need help understanding what to do please

Quick preface: Im taking pre-calculus at an online school and there is not much interaction from the instructor so I need some help or video links to help me understand how to solv this problem please.

Give an example of a function, f(x), with a domain of (0,5] and a range of [0,∞).

I have found NUMEROUS videos on how to get the domain and the range- but NO VIDEOS on how to use an existing domain and range to get the function.

Can someone please walk me through this? I presume that I do not need to graph this as an answer, but I need to write it out.

Basically this is how they started us out in the class- no foundation, no preface, just solve this... :( I appreciate anyone who is willing to help