Physics harmonics and wavelength problem. 10 points to explanation?

Third harmonic is 3/2 lambda.

So if 3/2 lambda = 6.2

then lambda = 6.2 * 2/3 = 62/15 = 4.13m

i'm no longer so familiar with the interdisciplinaries of physics, in spite of the indisputable fact that, it style of feels to me that shaking layers of salt and pepper is reducing order, a similar for smashing a coffe cup or including milk to coffee (dilution of the components and doubtless affliction). Conversely, my logic seems to lean in direction of the stuctural formation of crystals as a flow in direction of increasing order. hence my answer is D. Forming crystals in a answer. regrettably, there is the question of the complexities and conformaties between the milk and the coffee...i come across myself now meaning to earnings Physics.