It would be C because if you take out the four, the coefficients are multiples of 4 so it simplifies down.
Total sales = $3600
Commission earned on $3600 = $576
Commission rate can be calculated as = 
= 16%
Hence, commission rate is 16%
Answer:
This should be it
lmk if you have questions
y = x + 3.50.
Imagine, at the first day you have only one penny. Then tomorrow you have 2 pennies, next day you have 4 (2x2), next day you have 8 (4x2), next day you have 16 (8x2).... and so forth.
It looks like geometric sequence isn't it? (the ratio between the number of pennies that you have from the 2nd day and the 1st day is 2)
So, by using geometric sequence theorem we can total those pennies until day-27
S (total pennies at day-27) = (1)(2^27-1) / 2-1 = 2^26 pennies
So, you have 2^26 pennies.. a big number of pennies huh?=))
{The formula is: S = a( r^n-1) / r-1
Where:
a= the number of pennies that you've got at the 1st day
n= number of days you spent to collect those pennies)
r= the ratio of the number of pennies}
