Please show work and explain calculations.

Apple Inc.
CONSOLIDATED STATEMENTS OF OPERATIONS
(In millions, except number of shares which are reflected in thousands and per share amount)
	September 29, 2012	September 28, 2013
Net sales	$ 156,508	$ 170,910
Cost of sales	87,846	106,606
Gross margin	68,662	64,304
Operating expenses:
Research and development	3,381	4,475
Selling, general and
administrative	10,040	10,830
Total operating expenses	13,421	15,305
Operating income	55,241	48,999
Other income/(expense), net	522	1,156
Income before provision for
income taxes	55,763	50,155
Provision for income taxes	14,030	13,118
Net income	$ 41,733	$ 37,037

Requirements:
1. Calculate the $ change and % change from 2012 to 2013 (15 Points)
2. Calculate the common size % for each year using total revenues as your base amount (15 Points)
3. In what year, was the company able to retain a higher % of gross profit? Why do you think that was the case? (10 Points)
4. In what year, was the company able to retain a higher % of net income? Why do you think that was the case? (10 points)