The Following Are Included in Ace Auto Parts, Inc Below Are the Balances for December 31, 2013

The following are included in Ace Auto Parts, Inc.'s December 31, 2012 balance sheet:
$\begin{array}{|l|l|}\hline 50,000 & \text { Accounts Receivable } \\\hline 100,000 & \text { Building } \\\hline 60,000 & \text { Cash } \\\hline 130,000 & \text { Land } \\\hline 40,000 & \text { Accounts Payable } \\\hline 70,000 & \text { Notes Payable } \\\hline ? & \text { Stockholders Equity }\\\hline\end{array}$
Below are the balances for December 31, 2013:
$\begin{array}{|l|l|}\hline \$90,000 & \text { Accounts Receivable } \\\hline 100,000 & \text { Building } \\\hline 150,000 & \text { Cash } \\\hline 130,000 & \text { Land } \\\hline 60,000 & \text { Accounts Payable } \\\hline50,000 & \text { Notes Payable } \\\hline ? & \text { Stockholders Equity }\\\hline\end{array}$
Analyze the changes in these balances and determine net income for 2013, assuming that the only change to stockholders' equity is from net income.