we have that
Model A -----> 8
Model B -----> 7
Model C ----> 4
Model D ----> 5
total ------> 24
Frequency
Model A ------> 8/24=0.3333=33.33%
Model B -------> 7/24=0.2917=29.17%
Model C ------> 4/24=0.1667=16.67%
Model D -----> 5/24=0.2083=20.83%
Part B
Horizon Plan ------> A and C
so
total phones=total A +total C=8+4=12