Answer
a) 280 Hz
b) 70 Hz
c) 210 Hz
Work Step by Step
a) The next higher frequency is:
$140 \times 2 = 280\ Hz$
b) When the string is clamped, the equation changes from $f=\frac{v}{2}$ to $f=\frac{v}{4}$. Thus, we multiply the original fundamental frequency by 1/2 to find:
$=140 \times .5 = 70 \ Hz$
c) The next highest frequency is:
$=70 \times (2+1)=210\ Hz$
