Write an equation that models the linear situation:A train starts a trip of 420 miles and it travels at a steady (average) speed of 70 miles per hour.Instructions:DO NOT USE ANY SPACES between variables, constants, equals signs, and operation signs.For example, DO NOT enter f(x) = 2x + 1DO ENTER:f(x)=2x+1Put parentheses around constants that are fractions like this: y=(2/3)x-(1/2)You may use decimals IF the decimal values are exact. (You cannot use .33 for 1/3 because it is not exact, but you can use 0.25 for 1/4.)To write your equation, use the variables:t = time traveled (hours)d(t) = distance left to travel (miles)Equation: