The G string on a violin has a fundamental frequency of 196 Hz. It is 28.0 cm long and has a mass of 0.500 g. While this string is sounding, a nearby violinist effectively shortens the G string on her identical violin (by sliding her finger down the sting) until a beat frequency of 2.50 Hz is heard between the two strings. When this occurs, what is the effective length of her string?
____cm