For a recent year, McDonald's Company$-$owned restaurants had the following sales and expenses $($in millions$)$:

Sales $$21,200$

Food and packaging $$7,664$

Payroll $5,300$

Occupancy $($rent$,$ depreciation, etc.$)4,496$

General, selling, and administrative expenses $3,100$

$$20,560$

Income from operations $$640$

Assume that the variable costs consist of food and packaging, payroll, and $40\%$ of the general, selling, and administrative expenses.

a$.$ What is McDonald's contribution margin? Round to the nearest million. $($Give answer in millions of dollars.$)$

$fill in the blank $1$ million

b$.$ What is McDonald's contribution margin ratio?

fill in the blank $2\%$

c$.$ How much would income from operations increase if same$-$store sales increased by $$1,300$ million for the coming year, with no change in the contribution margin ratio or fixed costs? Round your answer to the closest million.

$fill in the blank $3$ million