CALCULATE THE AREA OF A TRIANGLE OF SIDES 13CM, AND 14CM,15cm

By using herons formula?
We get s=13+14+15/2
S=21cm
Now area=?s(s-a) (s-b) (s-c)?
?21(21-13)(21-14)(21-15)
?21(8)(7)(6)
?21(336)
?7056
84 cm? is the area