$3.($a$)$ A coupon bond has a face value of $$1,000$ and a coupon rate of $5\%,$ and its market price is $$900.$ What is the current yield of the bond? Briefly explain.

$($b$)$ Suppose you buy a one$-$year coupon bond with a $$100$ face value and a $40\%$ coupon rate for the market price of $$100$ in $2024$ and hold the bond till it matures. By the time that the bond matures in $2025$ suppose the price level doubles in value from its value in $2024.$ What is the actual return $($not rate of return$)$ you will get in terms of $2024$ dollars? Explain.