CREATE TABLE table_19204 ("Designation" TEXT, "Bus width  ( bits ) " FLOAT, "Channels" TEXT, "Clock rate  ( MHz ) " FLOAT, "Bandwidth  ( MB/s ) " FLOAT)

Name the least clock rate mhz when designation is rimm 4200
SELECT MIN("Clock rate (MHz)") FROM table_19204 WHERE "Designation" = 'RIMM 4200'
SELECT MIN("Clock rate (MHz)") FROM "table_19204" WHERE "Designation" = 'RIMM 4200'