Q$3$ A toroid has $1000$ turns and outer radius of $0\mathrm{.}2$ m and internal madius of $0\mathrm{.}10$ m $,$ earries a curment of $10$ A $.$ The magnetic field a distance of $0\mathrm{.}25$ m from its center is:

A$)4mT$

B$)6mT$

C$)10$ mT

D$)8$ mT