Question about Piecewise Functions

Let $f(x) = \lfloor x \lfloor x \rfloor \rfloor$ for $x \ge 0.$

(a) Find all $x \ge 0$ such that $f(x) = 1.$

(b) Find all $x \ge 0$ such that $f(x) = 3.$

(c) Find all $x \ge 0$ such that $f(x) = 5.$

(d) Find the number of possible values of $f(x)$ for $0 \le x \le 10.$