Answer
$B=0.00029T$
Work Step by Step
To find the magnetic field inside a solenoid, use the formula of $$B=\mu_oni$$ where $n$ is the number of turns per unit length. Calculating $n$ yields a value of $$n=\frac{N}{L}=\frac{200turns}{0.250m}=800turns/m$$ Substituting known values of $\mu_o=4\pi \times 10^{-7} H/m$, $n=800 turns/m$, and $i=0.29A$ yields a magnetic field of $$B=(4\pi \times 10^{-7} H/m)(800turns/m)(0.29A)=0.00029T$$
