This is in Differential Calculus. This is only multiple choice. Provide necessary solutions for each items. Follow the numbering thank you and Godbless.

7. Two cars are approaching an intersection which are perpendicular to each other. One car is moving at 9 m/'s and 75 meters from the intersection, the other car is moving at 6 m/'s and 100 meters from the intersection. How fast is the distance between them changing? A) 10.2 m/'s decreasing C) 11.4 m/'s increasing B) 8.4 m/'s decreasing D) 12.5 m/'s increasing 8. Water is poured into an upright right circular conical tank at the rate of 20 ft /sec. If the tank has a diameter of 8 ft across the top, and a height of 10 ft, how fast is the water surface rising inside the tank when the water in the tank is 6 ft deep? A) 1.28 fu/s C) 1.89 fu/s B) 2.12 fu/s D) 1.1I ft/s 9. A particle is moving along the curve y = 2r + e" such that its abscissa is increasing at the rate of 2 cm/'s (i.c., "- 2 cm/s). How fast is the y coordinate changing at the instant that its abscissa is 3 cm? A) 49.1 cm/'s C) 39.3 cm/'s B) 42.5 cm/'s D) 44.2 cm/s