# Shhhh! Don't give me the hint

Algebra Level 3

For positive real numbers $$a,b,c,d,$$ find the minimum value of the following expression:

$\displaystyle (a+b+c+d)\Bigl( \dfrac{25}{a} + \dfrac{36}{b} +\dfrac{81}{c} +\dfrac{144}{d} \Bigr).$

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