Explanation:

- The ratio of units manufactured for A, B, and C is given as 5:6:7.

- Let the common multiple be x. Therefore, units manufactured are: A = 5x, B = 6x, C = 7x.

- Units sold for A, C, and D follow a 6:8:5 ratio.

- 60% of A were sold, meaning 0.6 * 5x = 3x were sold.

- For C, 240 units were sold, and it is 8 parts in the ratio.

- Hence, the ratio multiple y for the sales ratio is 240/8 = 30.

- Therefore, number of total units sold of A = 6 * 30 = 180.

- Use the fact that 3x (sales of A) = 180 to solve for x: x = 60.

- Thus, manufactured units: A = 5x = 300, B = 6x = 360, C = 7x = 420.

- The average of units manufactured for A, B, and C = (300 + 360 + 420) / 3 = 360.

The correct answer is:

- Option 3: 360