# In an example of “call options”

The following is an excerpt from Introduction to the Mathematics of Finance by Roman:

As a more concrete example, suppose that IBM is selling for $\$100$per share at this moment. A$3$month call option on IBM with strike price$\$102$ is a contract between the buyer and the seller of the option that says that the buyer may (but is not required to) purchase $\color{blue}{\bf 100}$ shares of IBM from the seller for $\$102$per share at any time during the next$3$months. In this example is the number$\color{blue}{100}\$ in blue arbitrarily picked by the author? Is it relevant to the concept of "call option"?

Call options are usually standardized product: in the contract you can (but are not obliged to) buy a certain amount, which is specified. The most common quantity is 100 shares (see for example the description by J. Hull, Options, Futures, and Other Derivatives).

Yes it's arbitrary, when you agree on the condition you define the how many shares and the Strike price if the contract is not standard