Atriangle has sides with lengths: 6, 9, and 5. how do you find the area of the triangle using heron's formula?

Area of triangle=Δ=√s(s-a)(s-b)(s-c)
a=6
b=9
c=5
s=(a+b+c)/2
s=(6+9+5)/2
s=10
                          Δ=√10(10-6)(10-9)(10-5)
                          Δ=10√2 sq. units
                  OR
                            Δ=14.14 sq. units
                  

It should be a or d i’m not sure