Answer is: option4
\( \frac{12}{5} \)Solution:
\( V = s^3 \)
\(\frac{dV}{dt} = 3s^2 \frac{ds}{dt} \)
\( 12 = 3 \times (20)^2 \times \frac{ds}{dt} \)
\(\frac{ds}{dt} = \frac{12}{3 \times 400} = 0.01 \)
\( A = 6s^2 \)
\(\frac{dA}{dt} = 12s \frac{ds}{dt} \)
\(\frac{dA}{dt} = 12 \times 20 \times 0.01 \)
\(\frac{12}{5} \)