r = 2.24 + 0.06x
p= 2.89 +0.10x

In the equations above, r and p represent the price per gallon, in dollars, of regular and premium grades of gasoline,respectively, x months after January 1 of last
year. What was the cost per gallon, in dollars,of premium gasoline for the month in which the per gallon price of premium exceeded the per gallon price of regular by $0.93?