Rachel and Nicole are training to run a half-marathon. Rachel begins by running 30 minutes on the first day of training. Each day she increases the time she runs by 3 minutes. Nicole’s training follows the function f(x)=5x+30, where x is the number of days since the training began, and f(x) is the time in minutes she runs each day. What is the rate of change in minutes per day for the training program that has the least rate of change?