Solution:
\( \frac{dC}{dt} = 100t - 200\)
\( \frac{d^2C}{dt^2} = 100 > 0 \) thus Minimum
\( 0 = 100t - 200\)
\( t = 2 \)
\( C = 50(2)^2 -200(2) +10 000 \)
\( C = 9800\)