Quick, sign this!

Algebra Level 1

Back in 1995, Don Ho and Efrem Zimbalist Jr were at an autograph-signing event.

Don Ho signed 15 autographs per minute and made $5 per autograph.

Efrem Zimbalist Jr signed 4 autographs per minute and made $9 per autograph.

If they both signed for 10 minutes, how much more in dollars did Don Ho make than Efrem Zimbalist Jr?