A two variable linear program has the following characteristics: The objective function maximizes $7$X$1+122$; Constraint $1$ states that $x11$; constraint $2$ states that $x21$; constraint $3$ states that $x10$; constraint $4$ states that $x20.$ Which of the following statements is true about the linear program?

In the optimal solution, constraint $3$ has a slack of $0.$

In the optimal solution, constraint $1$ has a slack of zero and constraint $2$ has a surplus of $1.$

The optimal solution value is $19\mathrm{.}75.$

In the optimal solution, constraint $1$ has "slack variable ${?}^{\text{'}\text{'}}=0.$