Hi there!
We can use the following equation to calculate the magnetic field inside of a solenoid:
![B = \mu_0 ni](https://img.qammunity.org/2023/formulas/physics/high-school/lr15f2im6fta91s7ouzicvq1e76gdstqra.png)
B = Magnetic Field Strength (T)
n = number of loops PER LENGTH
i = current through solenoid (A)
μ₀ = Permeability of free space (4π × 10⁻⁷ Tm/A)
First, we can solve for 'n' given 'N' (total # of loops) and L (length of solenoid).
![n = (N)/(L) = (200)/(0.25) = 800](https://img.qammunity.org/2023/formulas/physics/high-school/xkw4f2xsqlss5jjw1ztsvipmtkovytdht9.png)
Now, we can calculate the magnetic field:
![B = (4\pi * 10^(-7)) (800)(.29) = \boxed{2.915 * 10^(-4) T}](https://img.qammunity.org/2023/formulas/physics/high-school/7vts36akynm9u5so8lokjgt3znqvhp9frz.png)