Riyadh Development is considering the potential of four different development projects. Each project would be completed in at most three years. The required cash outflow for each project is given in the table below, along with the net present value $($npv$)$ of each project to Riyadh, and the cash that is available each year.

$\backslash$table$[[,$Cash Outflow Required $($$million$),$Cash$],[,$Project $1,$Project $2,$Project $3,$Project $4,$Available $($$million$)],[$Year $1,9,7,6,11,28],[$Year $2,6,4,3,0,13],[$NPV$,30,16,22,14,]]$

Riyadh Development wants to select at least one of the project $1,2,$ or $3.$ Write the model finding which projects should be undertaken to maximize the net present value