Devin and Karissa are 210 feet apart when they start walking toward one another. They are walking at the same speed, so whenever Devin travels some number of feet, Karissa travels the same number of feet. Let x represent the number of feet each of them traveled.a. Write an expression in terms of x to represent the total number of feet Devin and Karissa have walked toward one another.b. Write an expression in terms of x to represent the distance (in feet) between Devin and Karissa.