A closely packed coil having 1000 turns has an average radius of $62.8 \mathrm{~cm}$. If current carried by $62.8 \mathrm{~cm}$ the wire of the coil is $1 \mathrm{~A}$ the value of magnetic field produced at the centre of the coil will be (permeability of free space $=4 \pi \times 10^{-7}$ $\mathrm{H} / \mathrm{m}$ ) nearly