SOLUTION
Given the question in the image, the following are the solution steps to answer the question.
STEP 1: Write the given functions
[tex]\begin{gathered} m^{\prime}(t)=-0.012t^2+0.2t \\ M^{\prime}(t)=-0.006t^2+0.6t^2 \end{gathered}[/tex]
STEP 2: Find m'(20) for subject A
[tex]\begin{gathered} When\text{ t=20,} \\ \int_0^{20}-0.012t^2+0.2t \\ Apply\text{ the sum/difference rule} \\ =-31.999999992+40=8.0000008 \\ \\ \therefore M^{\prime}(20)=8.00000008 \end{gathered}[/tex]
STEP 3: Find M'(20) for subject B
[tex]\begin{gathered} When\text{ t=20} \\ \int_0^{20}-0.006t^2+0.2t \\ =-15.999999996+40=24.00000004 \end{gathered}[/tex]
STEP 4: Find how many more words subject B memorizes more than subject A
[tex]\begin{gathered} Difference=Subject\text{ B - Subject A} \\ =24.00000004-8..00000008\approx16 \end{gathered}[/tex]
Hence, Answer is approximately 16 words