The Spread of a Contaminant Is Increasing in a Circular $r ( t ) = 2.25 \sqrt { t }$

The spread of a contaminant is increasing in a circular pattern on the surface of a lake.The radius of the contaminant can be modeled by $r ( t ) = 2.25 \sqrt { t }$ ,where r is the radius in meters and t is the time in hours since contamination. ​
Find a function that gives the area A of the circular lake in terms of the time since the spread began.
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A) $A \circ r ( t ) = 5.0625 \pi \sqrt { t }$
B) $A \circ r ( t ) = 2.25 \pi t$
C) $A \circ r ( t ) = 5.0625 t$
D) $A \circ r ( t ) = 5.0625 \sqrt { t }$
E) $A \circ r ( t ) = 5.0625 \pi t$