A tube open at one end and closed at the other end produces sound having a fundamental frequency of 350 Hz. If you now open the closed end, the fundamental frequency becomes

700 Hz

Explanation:

From the given information;

If we consider the formula for the frequency of an open-end tube; we have the formula:

For a closed-end tube;

However, the fundamental frequency of open end tube can be expressed as:

where;

Then; the fundamental frequency of the open end tube is:

= 2(350)

= 700 Hz

the answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this