Measuring the speed of sound in the ocean is an important part of marine research. One application is the study of climate change. The speed of sound depends on the temperature, salinity, and depth below the surface. For a fixed temperature of 25 degrees Celsius and salinity of 35 parts per thousand, the speed of sound is a function of the depth. At the surface, the speed of sound is 1534 meters per second. For each increase in depth by 1 kilometer, the speed of sound increases by 17 meters per second. What increase in the speed of sound is caused by a 4-kilometer increase in depth?