The average price of a gallon of gas in $2018$ increased $$0\mathrm{.}30(12\mathrm{.}4$ percent$)$ from $$2\mathrm{.}42$ in $2017$ to $$2\mathrm{.}72$ in $2018.$

Required:

$1.$ Conduct a horizontal analysis by calculating the year$-$over$-$year changes in each line item, expressed in dollars and in percentages for the income statement of Tiger Industries for the year ended December $31,2018($amounts in billions$).$

$2-$a$.$ Conduct a vertical analysis by expressing each line as a percentage of total revenues.

$2-$b$.$ Excluding income tax and other operating costs, did Tiger earn more gross profit per dollar of revenue in $2018$ compared to $2017?$