$3.$ Stock B price is $$40/$share$.$ You bought $500$ shares of stock B using $$15,000$ of your own money, borrowing the rest from your broker. The interest rate on the margin loan is $8\%$ APR. You broker also has a $25\%$ maintenance margin requirement.

a$)$ What is your return rate if stock price immediately changes to $$44?$

b$)$ If stock price drops immediately, at what stock price will you get the margin call?

c$)$ What is your return rate if stock price after one year changes to $$36?$ d$)$ If stock price drops after one year, at what stock price will you get the margin call?