Please walk me through the following question (the answer is 29.3%):

Suppose you purchase 100 shares of a stock on January 1st for $50/share with $3000 of your own money and $2000 borrowed from your broker at 6%. The stock doesnt pay dividends. The broker requires a maintenance margin percentage of 35%. If the stock price hits $30 on December 31st, then then the margin percentage in your account falls to______ and you will get a margin call.