NPV and Profitability Index

A company finds the following available projects:

$\backslash$table$[[$Project$,$Present Value of Benefits,Initial Investment$],[$A$,25,000,20,000],[$B$,85,000,70,000],[$C$,62,000,50,000],[$D$,47,000,50,000]]$

The net present value $($NPV$)$ of each project is given as follows:

$NPV=$ Present value $of$ benefits $-$ Initial invesstment.

$($a$)$ Suppose the company has no limit to the available funds today. Which projects should the company undertake based on NPV$?$

$($b$)$ Suppose the company has a limit in its fund: it can spend only up to $$70,000.$ Which projects should the company undertake?