48.29 IS NOT THE ANSWER BECAUSE I GOT IT WRONG

You have decided to short 400 shares of Shake Shack, which is currently trading for $50 per share. Assume your account already has $10,000 in t-bills which you can use as collateral. For short sales, your broker requires an initial margin of 50% and a maintenance margin of 40% and you must also set aside 100% of the cash proceeds as collateral. By how much could the stock price increase before you receive a margin call