Choosing which workers (limited number) to use in a binary assignment problem? First of all, I am not completely sure whether this problem belong to the category of assignment problems so feel free to correct me in this case.

The problem:

We are given a set of $m$ workers $A = \{ a_1, a_2,...a_m \}$ and a set of $n$ tasks $T = \{ t_1, t_2,...,t_n \}$. Each worker either can or cannot perform any given task and there is no cost associated with a task. The set of tasks that can be performed by a single worker $a_i$ is $T_{a_i} \subset T$. The set of tasks that can be performed by a subset of $s$ workers is given by the union of the tasks each individual worker can perform $\bigcup_{i=1}^{s} T_{a_i}$ (not necessarily the first $s$ workers).

The problem is to select $s$ workers such that the number of task that can be performed is maximized, i.e. maximize the number of elements in $\bigcup_{i=1}^{s} T_{a_i}$.

I couldn't find which category of problems this belong to, let alone any solutions. Any help in this matter would be greatly appreciated!
Your problem is known as maximum coverage.