(4.) The magnitude of the vector sum of two vectors a and b is 8u, and magnitude of b is 5u. If the direction of a is reversed, the magnitude of the vector sum becomes 10u. Find the angle between a and b

Awater-filled u-tube manometer is used to measure the pressure inside a tank that contains air. the water level in the u-tube on the side that connects to the tank is 5 ft above the base of the tank. the water level in the other side of the u-tube (which is open to the atmosphere) is 2 ft above the base. determine the pressure within the tank.