An Ideal Solenoid of Length $10 \mathrm {~cm}$ Consists of a Wire Wrapped Tightly Around a Wooden Core

Multiple Choice

An ideal solenoid of length $10 \mathrm {~cm}$ consists of a wire wrapped tightly around a wooden core. The magnetic field strength is $4.0 \mathrm {~T}$ inside the solenoid. If the solenoid is stretched to $25 \mathrm {~cm}$ by applying a force to it, what does the magnetic field become?

A) $20 \mathrm {~T}$
B) $4.0 \mathrm {~T}$
C) $10.0 \mathrm {~T}$
D) $1.6 \mathrm {~T}$