A Hospital Has a 4%-Saline Solution and an 12%-Saline Solution

Multiple Choice

A hospital has a 4%-saline solution and an 12%-saline solution on hand. How much of each should be used to prepare 640 cm ³ of 7%-saline solution?

A) 240 cm ³ of a 12%-saline solution,
400 cm ³ of a 4%-saline solution.
B) 220 cm ³ of a 12%-saline solution,
420 cm ³ of a 4%-saline solution.
C) 400 cm ³ of a 12%-saline solution,
240 cm ³ of a 4%-saline solution.
D) 340 cm ³ of a 12%-saline solution,
300 cm ³ of a 4%-saline solution.
E) 440 cm ³ of a 12%-saline solution,
200 cm ³ of a 4%-saline solution.