The calculated values of the expressions are
(a) P(8,4) = 1680
(b) C(8,4) = 70
How to determine the values of the expressions
From the question, we have the following parameters that can be used in our computation:
(a) P(8,4)
(b) C(8,4)
We can calculate P(8, 4) using the formula:

In this case, n = 8 and k = 4.
Plugging these values into the formula, we get:

We can calculate C(8, 4) using the formula:

So, we have

Hence, the calculated values of the expressions are (a) P(8,4) = 1680 and (b) C(8,4) = 70