Given $f ( x ) = \left\{ \begin{array} { l l } { a x ^ { 2 } + b \:\text { for } } & \:\:\:{ x < 0 } \\ { 2 a x + 5\: \text { for } } & { 0 \leq x < 1 } \\ { 3 x - b } \:\:\:\:\text { for } & \:\:\:{x \geq 1 } \end{array} \right.$, determine the values of $a$ and $b$ so that $f$ is a continuous function.