Question 4: 20 Marks In one theory of learning, the rate at which a course is memorized is assumed to be proportional to the product of the amount already memorized and the amount that is still left to be memorized. Assume that
Q
denotes the total amount of content that has to be memorized, and
I(t)
the amount that has been memorized after
t
hours. (4.1) Write down a differential equation for
l
, using
k
for the constant of proportionality. Also, write down the initial value
I_(0)
. (4.2) Draw the phase line of the model. (4.3) Use the phase line to sketch solution curves when the initial values are
I_(0)=Q,I_(0)=(Q)/(2)
, and
I_(0)=0
.