instruction: what is the since beginning of big 12 when last 10 meetings is ou, 7-3, neutral site is ou, 2-1, and last 5 meetings is bu, 3-2?
response: SELECT "Since Beginning of Big 12" FROM table_50605 WHERE "Last 10 Meetings" = 'ou, 7-3' AND "at Neutral Site" = 'ou, 2-1' AND "Last 5 Meetings" = 'bu, 3-2'