Assume we have a $11$ year $5\mathrm{.}68\%$ coupon bond selling for $$1,000$ and

callable at par with semi$-$annual compounding.$$ What would be the

EFFECTIVE DURATION if the interest rates could change by $50$ basis points

$($annually$)?$ The answer is $7\mathrm{.}9$ I need to know how to solve with excel.