For Exercises $5-8,(\text { a ) determine the number of slack variables }$ needed, (b) name them, and (c) use slack variables to convert each constraint into a linear equation.
$$
\begin{array}{ll}{\text { Maximize }} & {z=1.2 x_{1}+3.5 x_{2}} \\ {\text { subject to: }} & {2.4 x_{1}+1.5 x_{2} \leq 10} \\ {} & {1.7 x_{1}+1.9 x_{2} \leq 15} \\ {\text { with }} & {x_{1} \geq 0, \quad x_{2} \geq 0}\end{array}
$$