The 49ers advanced to their second Super Bowl in team history after becoming the first team ever to win 15 regular season games since the league expanded to a 16-game schedule in 1978. Much of the hype surrounding the team was their offense, which boasted five Pro Bowlers. Quarterback Joe Montana recorded 279 out of 432 completions for 3,630 yards, 28 touchdowns, and only 10 interceptions. Running back Roger Craig (American football) was one of the 49ers major weapons, both rushing and receiving. Craig was the teams second-leading rusher with 649 rushing yards and 7 touchdowns, and also caught 71 passes for 675 yards. Pro Bowl running back Wendell Tyler, who had rushed for a team record 1,262 yards during the regular season, recorded 7 rushing touchdowns, and also caught 28 passes for 230 yards and 2 touchdown receptions.  Fullback Earl Cooper also made an impact with 41 receptions for 459 yards and 4 touchdowns. Wide receivers Freddie Solomon and Dwight Clark also were deep threats, gaining a combined total of 1,617 yards and 16 touchdowns. Up front, three of the 49ers five starting offensive linemen, Randy Cross, Fred Quillan, and Keith Fahnhorst, had been selected to play in the Pro Bowl. Overall, San Franciscos offense finished the season ranked second in the NFL in scoring (475 points) and fourth in total yards (6,544).
Question: How many more touchdowns were scored by Joe Montana than by Roger Craig?
Answer: 21