Oil prices tumbled 4 percent on Monday, with Brent crude futures falling $3. 96, or 4. 1 percent, to $92. 82 by 0329 GMT after briefly slipping under the key support level of $90 earlier in the session. US West Texas Intermediate crude was at $85. 29 a barrel, down $4. 02, or 4. 5 percent. Both contra. .



