D). 9 ft is indeed the correct answer. The height of the ball at a horizontal distance of 10 feet is 9 ft.
a : b : c = 12 : 10 : 15. To explain, if b is defined as two-fifths of c, denoting this relationship as b =

, it follows that 2c = 5b. Substituting yields c =

. Similarly, with 4a = 3c, we can express a as

. By manipulating these fractions, we find a : c =

:

, simplifying to 4:5. For b and c, from prior relationships, b:c =

:

simplifies to 2:3. Noticing that if b equals 15, we derive a : c = 12 : 15 and b : c = 10 : 15, which leads us to the simplified ratio of a : b : c = 12 : 10 : 15.
Answer:
The blood donated by volunteers was
milliliters.
Step-by-step explanation:
The total count of volunteers was 32, and those who were unable to give blood was
.
Thus, the remaining volunteers who contributed blood equals: 
Each volunteer contributed 470 milliliters of blood.
The overall amount of blood donated totals
milliliters.
The student ought to fix the vehicle, as that would be more economical.