A visible light emits light with a wavelength of 4.00x10^-7m.
Calculate the frequency of the violet light.

a) 7.50x10^4Hz
b) 6.30x10^24Hz
c) 7.50x10^1Hz
d) 6.30x10^-1Hz

that would be because of both gravity and friction. so     c

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.