The final trading day of the month was cruel to most regional companies, especially Cerner Corp. Shares in the North Kansas City-based medical software firm fell below $80, closing at $75.66. Shares declined $4.61 on Friday. Kansas City Southern shares fell $1.49 to $29.70. Among the winners Friday, DST closed at $45.33, up 49 cents; and YRC Worldwide gained 2 cents to close at 93 cents. read more