Calculating Total Cost of Notebooks and Pens

Consider the expression representing the total cost $C$ of $n$ notebooks and $m$ pens, given by the formula:

$$C = 3n + 2m$$

If Peter decides to buy 4 notebooks and 5 pens, what is the total cost? You can represent the situation with the equation:

$$C = 3(4) + 2(5)$$

Calculate and simplify the expression to determine the total cost.