$23.$ A nonlinear function may contain a product of two variables.a$.$ Trueb. False$24.$ When applying nonlinear programming to portfolio selection, a trade$-$off is being made between the expected return and the risk associated with the investment.a$,$Trueb. False$25.$ Which of the following is an example of a nonlinear function?Profit $=5$x$-,+7$x$2--2$x$22$Profit$=8$XX$24$X$23$c$.$ Profit $=$ x$,+6$x$2+3$x$1$X$2$d$.$ All answer choices are correcte. None of the choices is correct