How many?

Slugs

The slug is a derived unit of mass in a weight-based system of measures, most notably within the British Imperial measurement system and the United States customary measures system. A slug is defined as the mass that is accelerated by 1 ft/s2 when a net force of one pound (lbf) is exerted on it.

Short Tons

The short ton is a mass measurement unit equal to 2,000 pounds (907.18474 kg). It is commonly used in the United States, where it is known simply as a ton.