You will need to use the Pythagorean Theorem and plug in the varibles. The rope is the hypotenuse of the right triangle formed, and the 40ft water is the vertical leg, which leaves the ocean floor to be the horizontal leg.[a^{2}+b^{2}=c^{2}\] \[a^{2}+40^{2}=140^{2}\] Then solve for a. \[a^{2}=18000\] \[a=134.164\]