When String A is played with String B, it creates a 3.0 Hz beat frequency. When String A is played with String C, it creates a 3.0 Hz beat frequency. If you play String B and C together, what beat frequency will they make? (There are two possible answers; give one.)

Certain bacteria (such as aquaspirillum magnetotacticum) tend to swim toward the earth’s geographic north pole because they contain tiny particles, called magnetosomes, that are sensitive to a magnetic field. if a transmission line carrying 100 a is laid underwater, at what range of distances would the magnetic field from this line be great enough to interfere with the migration of these bacteria? (assume that a field less than 5% of the earth’s field would have little effect on the bacteria. take the earth’s field to be 5.0 * 10-5 t, and ignore the effects of the seawater.)