Three friends are working on a fitness app that allows users to earn a certain number of points, depending on the number of minutes they spend on each activity. The table below shows how many minutes each person spent on each activity, and how many total points they earned.

Write a system of three equations that can be used to determine the number of points a player gets for a minute of each activity. Use the variables y, c and s to represent points per minute for yoga, cardio and strength.​