Quadrilateral Rivalry

Two sisters, Daniel and Sophia, were always rivels when it came to math competitions. One day, Daniel drews a quadrilateral $ABCD$ on the floor of his room, with $AB=8$ . After sneaking into Daniel's room, his sister, Sophia, drew the diagonals of this quadrilateral and labeled their point of intersection as $S$ . Wanting to challenge Daniel, she measured $SA, SB, SC,$ and $SD$ , and wrote these lengths on the quadrilateral: $SA=4, SB=5, SC=10, SD=4$ . After doing so, Sophia challenged Daniel to find the length of $CD^2$ . Find the correct answer Daniel should have given.