Please I will appreciate step by step maths process. All necessary information is given in the question don't ask for more. I will appreciate no gamble to this. If you take time to help with this my thumb is ready to go up!

A 20 year 5,000 bond that pays 4% annual coupons mature at par. It is purchased to yield 5% annual for the first 12 years and 6% annual thereafter. Calculate the amount for accumulation of discount for the 8th coupon 8, A 20 year 5,000 bond that pays 4% annual coupons mature at par. It is purchased to yield 5% annual for the first 12 years and 6% annual thereafter. Calculate the amount for accumulation of discount for the 8th coupon 8