Number of exams per semester = 5
Average of first four exams = 90
Therefore,
Total of first four exams = 90*4 = 360 marks
Based on 5 exams,
Average = 360/5 = 72
Answer: 
Step-by-step explanation:
Given, the exponential function
for a graph that includes (–3, 16) and (–1, 4).
On putting these points, we will have

Now,

since the multiplicative factor cannot be negative, so b= 0.5.
At b= 0.5

So, the required function is
.