Placeholders for fields such as "Last Name" and "Address" would be inserted into which
document in a mail merge?

Explanation:

The last name goes inside the main body of the mail specifically at the "closing block".

While the Address is inserted into the Subject Line specifically to the "To block"

what class is it and how much will you pay?

the answer to your question would be something called hertz. the unit of measurement called a hertz, which is one cycle per second, is used to measure clock speed. within one cycle, your computer processes, refreshes, or updates itself to the changes that it is going through. in the case of computer clock speed, one hertz equals one tick per second. the clock speed of computers is usually measured in megahertz (mhz) or gigahertz (ghz)