Which of the following mathematical relationships could be found in a linear programming model? $($Select all that apply.$)$

$($a$)1$A $+2$B $<=60$

$($b$)2$A $2$B $=50$

$($c$)1$A $6$B$2<=10$

$($d$)7$

A

$+2$B $>=15$

$($e$)1$A $+1$B $=7$

$($f$)2$A $+6$B $+1$AB $<=36$

For the relationships that are unacceptable for linear programs, state why.

$---$Select$---$

could not be found in a linear programming model because

$---$Select$---$

$.$