As was already said you may use linterp and cspline for part a). You may also use pspline or lspline. Don't get confused - all three are cubic splines! The "c"(cubic), "p"(parabolic) or "l"(linear) only refers to the behavior at the endpoints.
If the goal of a) are simply plots, you don't even have to use linterp. Simply plot vector y over vector x. by default the points will be connected by straight lines.
According to b) the following should get you in the right direction. As so often Mathcad offers different ways to achieve a goal.
For the rest you should show some efforts of your own.
Guess the label "Math Homework" would have been a better choice for the label.
