An oil tanker took 7.1hours to travel from City A to City B at an average speed of 60 MPH. If a passenger boat took 2 fewer hours than the oil tanker to complete the same journey, what was the average speed of the passenger boat?

The illuminance of a surface varies inversely with the square of its distance from the light source. if the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters, by how many meters should the distance of the surface from the source be increased to reduce its illuminance to 30 lumens per square meter?