Answer
The acceleration reaches its maximum value when
$$
0=m_{1}=m_{10}+\left(d m_{1} / d t\right) t=1.30 \mathrm{kg}+(-0.200 \mathrm{kg} / \mathrm{s}) t
$$
or $$t=6.50 \mathrm{\ s} $$
Work Step by Step
The acceleration reaches its maximum value when
$$
0=m_{1}=m_{10}+\left(d m_{1} / d t\right) t=1.30 \mathrm{kg}+(-0.200 \mathrm{kg} / \mathrm{s}) t
$$
or $$t=6.50 \mathrm{\ s} $$
