Keshawn is playing his favorite video game. The graph shows the number of levels Keshawn already completed, , and the total points he earned, , while playing the game. The line graph is titled Video Game. The x-axis is labeled Levels Completed and goes from zero to four by a scale of one. The y-axis is labeled Total Points and goes from zero to one hundred by a scale of twenty-five. A straight line that begins at the origin and passes through the points one comma twenty-five and two comma fifty is graphed. Write an equation in the form of that can be used to model the relationship. Enter the correct value of in the box to complete the equation.