iPhone sales from the 2nd quarter in 2007 through the 2nd quarter in 2008 can be approximated by S(t) = −390t2 + 3,300t

[answerhappygod]

iPhone sales from the 2nd quarter in 2007 through the 2nd
quarter in 2008 can be approximated by
S(t)
= −390t2 +
3,300t − 4,800 thousand
phones (2 ≤ t ≤ 6)
in quarter t. (t = 1 represents the
start of the first quarter of 2007.)†
A coordinate
plane is labeled "iPhone sales (thousands)." There is a curve
and five points.
(a)
Compute S'(t).
S'(t) =
How fast were the iPhone sales changing in
the second quarter of
2008 (t = 6)? (Be careful to give
correct units of measurement.)
S'(6) = thousand phones per quarter
(b)
According to the model, iPhone sales did which of the
following?
increased at a slower and slower rate during 2007 (the interval
[2, 4]).decreased at a slower and slower rate during 2007 (the
interval [2, 4]) increased at a faster and
faster rate during 2007 (the interval [2, 4])decreased at a faster
and faster rate during 2007 (the interval [2, 4])