Answer:
= 7.56 * 10^-9 W
Explanation:
1) v  =  √(T/m)
v is the velocity of a wave on the string
T is the Tension
m is the mass of a unit length ( mass of a 1 m length of the string)
  v =  f.λ
√(T/m) = fλ
√(195/m) = 260 * 0.6
we don't know m because we don't know the length
√(195 / m)   = 156 Â
 195/m     =  156²
 195 / m    =  24,336 Â
      m    =  195 / 24,336
      m    =  0.008 kg/m
now we know the mass of a unit length
m  =  M / l
M is the mass of the string
l is the length of the string
0.008 = Â 2.8 * 10^-3 Â / l
  l   =  2.8 * 10^-3 / 8 * 10-3
  l   =  2.8 / 8
  l   =  0.35 m
OK that's the answer, hope you understood.
2) Power on a unit area is 3.6 * 10^-6  W/m²
so to find the power on a specific area, Â just multiply the area by the sound intensity
assuming the ear's flat area is the specified value
power intercepted by ear = (3.6 * 10^-6 W/m²) *( 2.1 * 10^-3 m²)
                      = 7.56 * 10^-9 W
