Pay cash for 100 shares of a $50 stock	$5,000
Buy another 100 shares on margin	+$5,000
Total value	$10,000
Stock rises to $70	+$4,000
Total value when shares are sold	$14,000
Repay margin loan	–$5,000
Pay margin interest	–$400
Subtract initial cash investment	–$5,000
Profit	$3,600