Write a regular expression pattern that matches strings representing trains. A single letter stands for each kind of car in a train: Engine, Caboose, Boxcar, Passenger car, and Dining car. There are four rules specifying how to form trains. 1. One or more Engines appear at the front; one Caboose at the end. 2. Boxcars always come in pairs: BB, , etc. 3. There cannot be more than four Passenger cars in a series. 4. One dining car must follow each series of passenger cars. These cars cannot appear anywhere other than these locations. Here are some legal and illegal exemplars. EC Legal: the smallest train EEEPPDBBPDC Legal : simple train showing all the cars EEBB Illegal: no caboose (everything else OK) EBBBC Illegal: three boxcars in a row EEDBBC Illegal: more than four passenger cars in a row EEPPBBC Illegal: no dining car after passenger cars EEBBDC Illegal: dining car after box car Hint: my RE pattern was 16 characters.