Please show formula and workings

New South Wales Treasury has issued $1,000 face value, 25-year bonds that pay a coupon of 9.875 per cent semi-annually.

The current market rate for similar securities is 11 per cent.

Required

a What is the bonds current market value?

b What will be the bonds price if rates in the market (i) decrease to 9 per cent; (ii) increase to 12 per cent?

Suppose the bonds were to mature in 12 years. How would the interest rate changes in part b affect the bond prices?