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Let $\"\"$ be the amount in treasury bills which yeilds $\"\"$ simple intrest.

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Let $\"\"$ be the amount in treasury bonds which yeilds $\"\"$ simple interst.

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Let $\"\"$ be the amount in corporate bonds which yeilds $\"\"$ simple intrest.

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Since the total investment is $\"\"$ .

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$\"\"$ .

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Total income of Kelly is $\"\"$ .

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$\"\"$ .

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The investment on the treasury bills is to be $\"\"$ more than the investment in the corporate bonds.

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Therefore, $\"\"$ .

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Substiute $\"\"$ in equation $\"\"$ .

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$\"\"$

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Substiute $\"\"$ in equation $\"\"$ .

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$\"\"$

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$\"\"$

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Multiple to each side the equation $\"\"$ by $\"\"$ .

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$\"\"$

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Add equation $\"\"$ and equation $\"\"$ to eliminate $\"\"$ .

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$\"\"$

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Substiute $\"\"$ in $\"\"$ .

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$\"\"$

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Substiute the value $\"\"$ and $\"\"$ in equation $\"\"$ .

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$\"\"$

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The solution is $\"\"$ and $\"\"$ .

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Therefore, kelly should invest $\"\"$ in treasury bills, $\"\"$ in treasury bonds and $\"\"$ in corporate bonds.

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Kelly should invest $\"\"$ in treasury bills, $\"\"$ in treasury bonds and $\"\"$ in corporate bonds.