Please solve asap. thanks

1. A U-tube contains liquid of unknown density. An oil of density 840 kg/m3 is poured into one arm of the tube until the oil column is 11.5 cm high. The oil-air interface is then 4.0 cm above the liquid level in the other arm of the U-tube. Find the density of the liquid. kg/m3 2. What is the smallest number of whole logs (density = 765 kg/m3, radius = 0.077 m, length = 2.85 m) that can be used to build a raft that will carry 5 people, each of whom has a mass of 86.5 kg? logs 3. A spring is attached to the bottom of an empty swimming pool, with the axis of the spring oriented vertically. An 8.60-kg block of wood (density = 640 kg/mo) is fixed to the top of the spring and compresses it. Then the pool is filled with water, completely covering the block. The spring is now observed to be stretched twice as much as it had been compressed. Determine the percentage of the block's total volume that is hollow. Ignore any air in the hollow space. % 4. A solid cylinder (radius = 17.5 cm, height = 13.5 cm) has a mass of 11.04 kg. This cylinder is floating in water. Then oil (density = 725 kg/m3) is poured on top of the water until the situation shown in the drawing results. How much of the height of the cylinder is in the oil? cm Oi Water 5. A lead block is suspended by means of a string from the underside of a 9.00 kg block of wood of density of 680 kg/m. If the upper surface of the wood is just level with the water, what is the mass of the lead block?(The density of lead is 11340 kg/m3) kg