Answer :
Here, (c)ost and (g)allons vary directly so we have:
c = k times g
And since we have the price per gallon, we have that "k" -> 1.89
So,
c = (1.89)(g)
c = k times g
And since we have the price per gallon, we have that "k" -> 1.89
So,
c = (1.89)(g)