QBASIC PROGRAM TO FIND AREA OF 4 WALLS(SUB)

DECLARE SUB AREA (L ,B ,H )
CLS
INPUT" ENTER LENGTH ";L
INPUT" ENTER BREADTH ";B
INPUT" ENTER HEIGHT ";H
CALL AREA (L ,B ,H)
END

SUB AREA (L ,B ,H)
A = 2* H * (L +B )
PRINT" AREA  OF 4 WALLS ";A
END SUB