[originaltext]A company in San Francisco, California, has found a way to turn u

A company in San Francisco, California, has found a way to turn used plastic bottles into women’s shoes. Every day, millions of Americans drink water and other liquids from plastic bottles. More than 60 million of them are thrown away each day. Many of the plastic bottles end up in landfills or are burned with other waste products. A San Francisco start-up company called Rothy’s, however, turns this plastic waste into environmentally friendly shoes. Roth Martin is the company’s co-founder. He explains how they turn plastic into soft material for your feet. They take the plastic, clean it, and break it down into small pieces. Then they press it through a device that makes soft fibers. Those fibers are then combined, or knit together. This is done by a three-dimensional knitting machine. It is designed to reduce waste while making the shoes. The knitted fabric and the inner part of the shoe are then attached to the shoe’s outer part, called the sole. Rothy’s shoes are sold online. They cost either $125 or $145 per pair, depending on the design. After American actress Gwyneth Paltrow discovered them last year, the demand for the shoes grew. Martin says there is no shortage of material to fill that demand. When the environmentally friendly shoes wear out, customers can return them at no cost to a company that uses the recycled materials to make other products. For now, the shoes are only available to be shipped in the United States. However, the company says it will add international shipping in the near future.
Questions 16 to 18 are based on the passage you have just heard.
16. What does the company Rothy’s do?  
17. What is the three-dimensional knitting machine designed for?
18. What determines the cost of the environmentally friendly shoes?