Answer: Option 'A' is correct
Explanation:
Since we have given that
Total money Gillian spend on both cotton shirts and wool shirts = $300
Cost of per cotton shirt = $15
Cost of per wool shirt = $ 20
According to question,
The number of wool shirts Gillian will buy will be at least 3, but less than half the number of cotton shirts she buys.
So, by option when we use the data of Option 'A'
Number of cotton shirts =13
Cost incurred on cotton shirt is given by

Number of wool shirts = 4
Cost incurred on wool shirt is given by

Total cost incurred on both the shirts is given by

If we use option 'B' we spend only $230
If we use option 'C' , it does not satisfy the question as it is mentioned in the question that number of wool shirt must be less than half of number of cotton shirt
If we use option 'D' , we spend $325 which is much higher than $300
Hence , option "A" is correct.