I had quiz last week and it says: suppose algorithms $A_1$ and $A_2$ have worst-case time bound $p$ and $q$, respectively. Suppose algorithm $A_3$ consists of applying $A_2$ to the output of $A_1$. (The input for $A_3$ is the input for $A_1$.) Give a worst-case time bound for $A_3$.

How could I calculate the worst case based on the given info?