PLEEEASE HELP ME ASAP *will ofc give brainliest*

B) 5

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Work Shown:

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Notes:

In line 2, I replaced r with 2t because the radius r is increasing at a rate of 2 cm per second. So if t is the number of seconds, then 2t is the radius in cm at time t.In line 4, I multiplied both sides by 3 to clear out the fractions. On the next line, I divided both sides by 4pi.