Printer ink cartridges cost $19 each. The company that sells the ink cartridges charges a flat shipping rate of $7.50, no matter how many ink cartridges you buy. Write an algebraic expression that describes the total cost for a single order of `x`, cartridges.

To find the total cost for an order of \( x \) ink cartridges, we can break down the costs as follows:

1. Each ink cartridge costs $19.
2. There is a flat shipping fee of $7.50, regardless of the number of cartridges ordered.

For \( x \) cartridges, the cost for the cartridges is \( 19x \), and the shipping cost is \( 7.50 \).

Therefore, the algebraic expression for the total cost \( C \) as a function of the number of cartridges \( x \) is:

\[
C = 19x + 7.50
\]