QBASIC PROGRAM TO FIND AREA OF 4 WALLS(FUNCTION)

DECLARE FUNCTION AREA(L, B, H)
CLS
INPUT"ENTER LENGTH"; L
INPUT" ENTER BREADTH"; B
INPUT"ENTER HEIGHT"; H
PRINT"AREA OF 4 WALLS"; AREA(L,B,H)
END

FUNCTION AREA(L, B, H)
A= 2 * H * ( L+B)
AREA= A
END F