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 Combustion Petroleum 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 Combustion earn more gross profit per dollar of revenue in $2018$ compared to $2017?$Req $1$

Req $2A$

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 Combustion Petroleum for the year ended December $31,2018($amounts in

billions$).($Decreases should be indicated by a minus sign. Enter your answers in billions $($i$.$e$.,10,000,000,000$ should be

entered as $10).$ Round percentage values to $1$ decimal place.$)$