Question=> How many offices are on the first floor of the building?
Statement 1: There is a total of 9500 square feet of office space on the first floor of the building.
There are so many ways in which we can split 9500 into the sum of 200, 300 and/or 350. Hence, statement 1 is NOT SUFFICIENT.

Statement 2: Item of the offices on the first floor have floor areas of 350 square feet.
This means that the total number of offices on the first floor is greater than 10 but we do not know the exact value. Hence, statement 2 is NOT SUFFICIENT.

Combining both statements together=>
Statement 1: Total office space = 9500 square feet
Statement 2: Ten office space = 350 square feet
9500 - (350 * 10) = 9500 - 3500 = 6000 square feet out of the 9500 square feet office space on the first floor.
10 offices have an area of 350 square feet. The remaining 6000 square feet can be split into the sum of 200 and/or 300 in multiple ways. Hence, no definite values.

Therefore, both statements together are NOT SUFFICIENT. Hence, Option E is the correct answer.