\textbf{124.} What is $\displaystyle\int_1^{16} [\sqrt{x}]\, dx$? (The symbol $[\,]$ denotes the floor function.) \vspace{0.3cm} (1) $30$ \hfill (2) $31$ \hfill (3) $32$ \hfill (4) $34$ \vspace{0.5cm}