The behaviour of the sum:
$$\displaystyle\sum_{n \leq x} \frac{\varphi(n)}{n}$$
is well-studied. However, I am interested in the behaviour of the following sum, and haven't been able to find any material about it online:
$$\displaystyle\sum_{n \leq x} \Big( \frac{\varphi(n)}{n} \Big)^2$$
Alternatively, it seems like this sum can be expressed in the form:
$$\displaystyle\sum_{n \leq x} \displaystyle\sum_{d|n, \ e|n} \frac{\mu(e) \mu(d)}{de}$$
Is anything known about the behaviour of this partial sum?
Note: I would really appreciate if anyone answering this question didn't give me an outright answer, maybe just a small hint to point me in the right direction, as I'd really like to figure this out myself. Thank you!