RIVERDALE, MD -- It's her last semester of senior year at Parkdale High in Prince George's County, and Carla Riviera figured she'd struggle to make little motors in tech class.

She was born in El Salvador without a left wrist or arm.

But her teacher in Riverdale, Md. had an idea to have a whole section of the class devoted to building Carla a new arm with a 3D printer.

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When Karen Bogoski, asked Carla if that sounded like a good idea, she said Carla broke down and cried happy tears.

Bogoski spent $70 of her own money for fishing line and the plastic filament in the pink and blue Carla wanted. She convinced a dentist to donate some rubber bands. The software for the printer was free online. It took two months to piece it together.

"I told her I wanted to throw it against the wall a couple of times," said Bogoski.

When it was finally finished, Carla could scarcely believe it.

"I got emotional," said Carla.

She's spent a lot of time practicing.

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"Children are the largest demographic that need prosthetics. But because they grow so fast, they can't afford them," said Bogoski.

She's is already plotting how to make an even better arm.

"It would just be adding motors and servos. I don't know how she would control it."

Carla is planning for college and new opportunities.

"It's amazing for me," she said.

More miracles may be coming. Prince George's County is hoping to buy 3D printers for every high school.