A spring of spring constant 3.00 X 10^4 N/m is between a rigid beam and the output piston of a hydraulic lever. An empty container with negligable mass sits on the input piston. The input piston has area Ai and the output piston has area 18.0Ai. Initially the spring is at its rest length. How many kilograms of sand must be (slowly) poured into the container to compress the spring by 5.00cm?