SELECT T1.Age FROM driver AS T1 JOIN race AS T2 ON T1.Driver_ID  =  T2.Driver_ID GROUP BY T1.Driver_ID ORDER BY COUNT(*) DESC LIMIT 1
Please show the age of the driver who participated in the most number of races.
CREATE TABLE "driver" (
"Driver_ID" int,
"Driver_Name" text,
"Entrant" text,
"Constructor" text,
"Chassis" text,
"Engine" text,
"Age" int,
PRIMARY KEY ("Driver_ID")
);
CREATE TABLE "race" (
"Road" int,
"Driver_ID" int,
"Race_Name" text,
"Pole_Position" text,
"Fastest_Lap" text,
"Winning_driver" text,
"Winning_team" text,
"Report" text,
PRIMARY KEY ("Road"),
FOREIGN KEY (`Driver_ID`) REFERENCES `driver`(`Driver_ID`)
);
INSERT INTO  "driver" VALUES ("1","Ernst-Günther Burggaller","German Bugatti Team","Bugatti","Bugatti T35B","2.3 L8","18");
INSERT INTO  "race" VALUES ("2","1","Monterey Festival of Speed","James Hinchcliffe","Douglas Soares","James Hinchcliffe","Forsythe Pettit Racing","Report");