Chapter 9 - Section 9.3 - The Parabola - Exercise Set - Page 998: 76

$\frac{25}{6}\approx4.17\ ft$

Step 1. Let the dish face up and its bottom be the origin. The equation of the parabola can be written as $x^2=4py$ Step 2. The receiver should be at the focus. Thus we have $p=6$ Step 3. One edge point of the dish is $(10,y)$. We have $10^2=4(6)y$, which gives $y=\frac{25}{6}\approx4.17\ ft$, the depth of the dish.