Your answer tired person is: 56.25
A=(a+b/2) x h
a = 8
b = 14
h = 14
(8+14/2) x 14
(22/2) x 14
11 x 14 = 154
The answer is 154
Check the picture below
so.. .hmmm the vertex is at the origin... and we know the parabola passes through those two points... let's use either.. say hmmm 100,-50, to get the coefficient "a"
keep in mind that, the parabolic dome is vertical, thus we use the y = a(x-h)²+k version for parabolas, which is a vertical parabola
as opposed to x = (y-k)²+h, anyway, let's find "a"

now.. .your choices, show.... a constant on the end.... a constant at the end, is just a vertical shift from the parent equation, the equation we've got above.. is just the parent equation, since we used the origin as the vertex, it has a vertical shift of 0, and thus no constant, but is basically, the same parabola, the one in the choices is just a shifted version, is all.
Is it just x=b-cd
If so
cd=b-x
÷d. ÷d
C=b-x/d