Answer
$0.5T$, to one significant figure.
Work Step by Step
Use equation 20–8 for the magnetic field inside a solenoid, but replace $\mu_o$ with the permeability of iron.
$$B=\frac{\mu NI}{\mathcal{l}}=\frac{(3000)(4\pi \times10^{-7} T\cdot m/A)(380)(0.350A)}{1m}$$
$$=0.5T$$
