It’s been 50 years since the Rao family opened Mr. Lemon in Providence. Customers come to the tiny white building on Hawkins Street for the frozen lemonade, and many return because they feel like family. Colleen, Joe, and Janice Rao know almost everyone – and their favorite flavors. They talk with Ed about the business and their first year serving lemonade without their mother, Eileen Rao. Got a story about Mr. Lemon? Email us at rinews@globe.com.