For the coming year, Tycho Corp. expects to report earnings per share of $4 (unchanged from last year) and a cash dividend per share of $1. It is also expected that they will be able to maintain the same dividend payout ratio and earn a rate of return on equity of 10% for the foreseeable future. What is the company's sustainable growth rate, given its return on equity and its plowback ratio?

1. 2.5%

2. 10%

3. 40%

4. 7.5%