There are many ordered pairs that are solutions to the equation but here are the few; (0,2.5), (2,2), (4,1.5), (-2,3), (-4,3.5), (-6,4), (6,1), (8,0.5), etc...
58 inches. 4 feet is equal to 48 inches and if the rock is sinking at -2 feet an second for 5 seconds, then that is -10 inches and the absolute value of -10 is 10 so 10+48=58