The grades of six students are given by the equations below, where time is measured in weeks since the first midterm exam.

(1) $P=85(0.92)^t$
(2) $P=68(.95)^t$
(3) $P=85(1.001)^t$
(4) $P=75(1.005)^t$
(5) $P=93(1.03)^t$
(6) $P=72(0.85)^t$
a) Alex's grade has been decreasing since the first exam. Which formula(s) could represent her grade?
A. 1
B. 2
C. 3
D. 4
E. 5
F. 6

b) Which student's grade is falling the fastest?
A. 1
B. 2
C. 3
D. 4
E. 5
F. 6

c) Umar's grade has been rising since the first exam; Which formula(s) could represent his grade?
A. 1
B. 2
C. 3
D. 4
E. 5
F. 6

d) Which student's grade is rising the fastest?
A. 1
B. 2
C. 3
D. 4
E. 5
F. 6

e) Karan came out of the first exam with a 85% in the class; which formula(s) could represent his grade?
A. 1
B. 2
C. 3
D. 4
E. 5
F. 6

Hint: